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Squares And Square Roots

Class 8th Mathematics RD Sharma Solution
Exercise 3.1
  1. (i) 484 (ii) 625 (iii) 576 (iii) 576 (iv) 941 (v) 961 (vi) 2500 Which of the…
  2. Show that each of the following numbers is a perfect square. Also find the…
  3. Find the smallest number by which the given number must be multiplied so that…
  4. Find the smallest number by which the given number must be divided so that the…
  5. 11, 12, 16, 32, 36, 50, 64, 79, 81, 111, 121 Which of the following numbers are…
  6. Using prime factorization method, find which of the following numbers are…
  7. By what number should each of the following numbers by multiplied to get a…
  8. By What numbers should each of the following be divided to get a perfect square…
  9. Find the greatest number of two digits which is a pefect square.
  10. Find the least number of three disgits which is perfect square.
  11. Find the smallest number by which 4851 must be multiplied so that the product…
  12. Find the smallest number by which 28812 must be divided so that it becomes a…
  13. Find the smallest number by which 1152 must be divided so that it becomes a…
Exercise 3.2
  1. The following numbers are not perfect squares. Give reason. (i) 1547 (ii) 45743…
  2. Show that the following numbers are not, perfect squares: (i) 9327 (ii) 4058…
  3. The square of which of the following numbers would be an old number? (i) 731…
  4. What will be the units digit of the squares of the following numbers? (i) 52…
  5. Observe the following pattern 1+3 = 2^2 1+3+5 = 3^2 1+3+5+7 = 4^2 And write the…
  6. 2^2 - 1^2 = 2+1 3^2 - 2^2 = 3+2 4^2 - 3^2 = 4+3 5^2 - 4^2 = 5+4 And find the…
  7. Which of the following triplets are Pythagorean? (i) (8, 15, 17) (ii) (18, 80,…
  8. (1 x 2) + (2 x 3) = 2 x 3 x 4/3 (1 x 2) + (2 x 3) + (3 x 4) = 3 x 4 x 5/3 (1 x…
  9. Observe the following pattern 1 = 1/2 1 x (1+1) 1+2 = 1/2 2 x (2+1) 1+2+3 = 1/2…
  10. Observe the following pattern 1^2 = 1/6 [1 x (1+1) x (2 x 1+1)] 1^2 + 2^2 = 1/2…
  11. Which of the following numbers are squares of even numbers? 121, 225, 256, 324,…
  12. By just examining the units digits, can you tell which of the following cannot…
  13. Which of the numbers for which you cannot decide whether they are squares.…
  14. Write five numbers which you cannot decide whether they are square just by…
  15. Write true (T) or false (F) for the following statements. (i) The number of…
Exercise 3.3
  1. Find the squares of the following numbers using column method. Verify the result…
  2. Find the squares of the following numbers using diagonal method: (i) 98 (ii) 273…
  3. (i) 127 (ii) 503 (iii) 450 (iv) 862 (v) 265 Find the squares of the following…
  4. (i) 425 (ii) 575 (iii)405 (iv) 205 (v) 95 (vi) 745 (vii) 512 (viii) 995 Find the…
  5. Find the squares of the following numbers using the identify (a+b)^2 = a^2 +…
  6. Find the squares of the following numbers using the identity (a-b)^2 = a^2 -…
  7. Find the squares of the following numbers by visual method: (i) 52 (ii) 95 (iii)…
Exercise 3.4
  1. Write the possible units digits of the square root of the following numbers.…
  2. Find the square root of each of the following by prime factorization. (i) 441…
  3. Find the smallest number by which 180 must be multiplied so that it becames a…
  4. Find the smallest number by which 147 must be multiplied so that it becomes a…
  5. Find the smallest number by which 3645 must be divided so that it becomes a…
  6. Find the smallest number by which 1152 must be divided so that it becomes a…
  7. The product of two numbers is 1296. If one number is 16 times the other, find…
  8. A welfare association collected Rs 202500 as donation from the residents. If…
  9. A society collected Rs 92.16. Each member collected as many paise as there were…
  10. A society collected Rs 2304 as fees from its students. If each student paid as…
  11. The area of a square field is 5184 m^2 . A rectangular field, whose length is…
  12. Find the least square number, exactly divisible by each one of the numbers: (i)…
  13. Find the square roots of 121 and 169 by the method of repeated subtraction.…
  14. Write the prime factorization of the following numbers and hence find their…
  15. The students of class VIII of a school donated Rs 2401 for PMs National Relief…
  16. A PT teacher wants to arrange maximum possible number of 6000 students in a…
Exercise 3.5
  1. Find the square root of each of the following by long division method: (i) 12544…
  2. Find the least number which must be subtracted from the following numbers to…
  3. Find the least number which must be added to the following numbers to make them…
  4. Find the greatest number of 5 digits which is a perfect square.
  5. Find the least number of 4 digits which is a perfect square.
  6. Find the least number of six digits which is a perfect square.
  7. Find the greatest number of 4 digits which is a perfect square.
  8. A General arranges his soldiers in rows to form a perfect square. He finds that…
  9. The area of a square field is 60025m^2 . A man cycles along its boundary at 18…
  10. The cost of leveling and turning a square lawn at Rs 2.50 per m^2 is Rs13322.50…
  11. Find the greatest number of three digits which is a perfect square.…
  12. Find the smallest number which must be added to 2300 so that it becomes a…
Exercise 3.6
  1. Find the square root of: (i) 441/961 (ii) 324/841 (iii) 4 29/29 (iv) 2 14/25 (v)…
  2. Find the value of: (i) root 80/root 405 (ii) root 441/root 625 (iii) root…
  3. The area of a square field is 80 244/729 square metres. Find the length of each…
  4. The area of a square field is 30 1/4 m^2 . Calculate the length of the side of…
  5. Find the length of a side of a square playground whose area is equal to the area…
Exercise 3.7
  1. 84.8241 Find the square root of the following numbers in decimal form:…
  2. 0.7225 Find the square root of the following numbers in decimal form:…
  3. 0.813604 Find the square root of the following numbers in decimal form:…
  4. 0.00002025 Find the square root of the following numbers in decimal form:…
  5. 150.0625 Find the square root of the following numbers in decimal form:…
  6. 225.6004 Find the square root of the following numbers in decimal form:…
  7. 3600.720036 Find the square root of the following numbers in decimal form:…
  8. 236.144489 Find the square root of the following numbers in decimal form:…
  9. 0.00059049 Find the square root of the following numbers in decimal form:…
  10. 176.252176 Find the square root of the following numbers in decimal form:…
  11. 9998.0001 Find the square root of the following numbers in decimal form:…
  12. 0.00038809 Find the square root of the following numbers in decimal form:…
  13. What is that fraction which when multiplied by itself gives 227.798649?…
  14. The area of a square playground is 256.6404 square meter. Find the length of…
  15. What is the fraction which when multiplied by it self gives 0.00053361?…
  16. Simplify: (i) root 59.29 - root 5.29/root 59.29 + root 5.29 (ii) root 0.2304 +…
  17. Evaluate root 50625 and hence find the value of root 506.25 + root 5.0625…
  18. Find the value of root 103.0225 and hence find the value of (i) root 10302.25…
Exercise 3.8
  1. Find the square root of each of the following correct to three places of…
  2. Find the square root of 12.0068 correct to four decimal places.
  3. Find the square root of 11 correct to five decimal places.
  4. Give that: root 2 = 1.414 , root 3 = 1.732 , root 5 = 2.236 root 7 = 2.646…
  5. Given that root 2 = 1.414 , root 3 = 1.732 , root 5 = 2.236 and root 7 = 2.646…
Exercise 3.9
  1. 7 Using square root table, find the square roots of the following:…
  2. 15 Using square root table, find the square roots of the following:…
  3. 74 Using square root table, find the square roots of the following:…
  4. 82 Using square root table, find the square roots of the following:…
  5. 198 Using square root table, find the square roots of the following:…
  6. 540 Using square root table, find the square roots of the following:…
  7. 8700 Using square root table, find the square roots of the following:…
  8. 3509 Using square root table, find the square roots of the following:…
  9. 6929 Using square root table, find the square roots of the following:…
  10. 25720 Using square root table, find the square roots of the following:…
  11. 1312 Using square root table, find the square roots of the following:…
  12. 4192 Using square root table, find the square roots of the following:…
  13. 49555 Using square root table, find the square roots of the following:…
  14. 99/144 Using square root table, find the square roots of the following:…
  15. 57/169 Using square root table, find the square roots of the following:…
  16. 101/169 Using square root table, find the square roots of the following:…
  17. 13.21 Using square root table, find the square roots of the following:…
  18. 21.97 Using square root table, find the square roots of the following:…
  19. 110 Using square root table, find the square roots of the following:…
  20. 1110 Using square root table, find the square roots of the following:…
  21. 11.11 Using square root table, find the square roots of the following:…
  22. The area of a square field is 325m^2 . Find the approximate length of one side…
  23. Find the length of a side of a square, whose area is equal to the area of a…

Exercise 3.1
Question 1.

Which of the following numbers are perfect squares?

(i) 484 (ii) 625

(iii) 576 (iii) 576

(iv) 941 (v) 961

(vi) 2500


Answer:

(i) 484


Resolving 484 into prime factors we get,


484 = 2 × 2 × 11 × 11


Now,


Grouping the factors into pairs of equal factors, we get:


484 = (2 × 2) × (11 × 11)


We observe that all are paired so,


484 is a perfect square


(ii) 625


Resolving 625 into prime factors we get,


625 = 5 × 5 × 5 × 5


Now,


Grouping the factors into pairs of equal factors, we get:


625 = (5 × 5) × (5 × 5)


We observe that all are paired so,


625 is a perfect square


(iii) 576


Resolving 576 into prime factors we get,


576 = 2 × 2 × 2 × 2 × 2 × 2 × 3 × 3


Now,


Grouping the factors into pairs of equal factors, we get:


576 = (2 × 2) × (2 × 2) × (2 × 2) × (3 × 3)


We observe that all are paired so,


576 is a perfect square


(iv) 941


Resolving 941 into prime factors we get,


941 = 941 × 1


Now,


As 941 itself is a prime number


Hence,


It do not have a perfect square


(v) 961


Resolving 961 into prime factors we get,


961 = 31 × 31


Now,


Grouping the factors into pairs of equal factors, we get:


961 = (31 × 31)


We observe that all are paired so,


961 is a perfect square


(vi) 2500


Resolving 2500 into prime factors we get,


2500 = 2 × 2 × 5 × 5 × 5 × 5


Now,


Grouping the factors into pairs of equal factors, we get:


2500 = (2 × 2) × (5 × 5) × (5 × 5)


We observe that all are paired so,


2500 is a perfect square



Question 2.

Show that each of the following numbers is a perfect square. Also find the number whose square is the given number in each case:

(i) 1156

(ii) 2025

(iii)14641

(iv) 4761


Answer:

(i) 1156


Resolving 1156 into prime factors we get,


1156 = 2 × 2 × 17 × 17


Now, grouping the factors into pairs of equal factors


We get,


1156 = (2 × 2) × (17 × 17)


As all factors are paired


Hence, 1156 is a perfect square


Again,


1156 = (2 × 17) × (2 × 17)


= 34 × 34


= (34)2


Thus, 1156 is a square of 34


(ii) 2025


Resolving 2025 into prime factors we get,


2025 = 3 × 3 × 3 × 3 × 5 × 5


Now, grouping the factors into pairs of equal factors


We get,


2025 = (3 × 3) × (3 × 3) × (5 × 5)


As all factors are paired


Hence, 2025 is a perfect square


Again,


2025 = (3 × 3 × 5) × (3 × 3 × 5)


= 45 × 45


= (45)2


Thus, 2025 is a square of 45


(iii)14641


Resolving 14641 into prime factors we get,


14641 = 11 × 11 × 11 × 11


Now, grouping the factors into pairs of equal factors


We get,


14641 = (11 × 11) × (11 × 11)


As all factors are paired


Hence, 14641 is a perfect square


Again,


14641 = (11 × 11) × (11 × 11)


= 121 × 121


= (121)2


Thus, 14641 is a square of 121


(iv) 4761


Resolving 4761 into prime factors we get,


4761 = 3 × 3 × 23 × 23


Now, grouping the factors into pairs of equal factors


We get,


4761 = (3 × 3) × (23 × 23)


As all factors are paired


Hence, 4761 is a perfect square


Again,


4761 = (3 × 23) × (3 × 23)


= 69 × 69


= (69)2


Thus, 4761 is a square of 69



Question 3.

Find the smallest number by which the given number must be multiplied so that the product is a perfect square:

(i) 23805

(ii) 12150

(iii) 7688


Answer:

(i) 23805


Resolving 23805 into prime factors, we get


23805 = 3 × 3 × 23 × 23 × 5


Obtained factors can be paired into equal factors except for 5


To pair it equally multiply with 5


23805 × 5 = 3 × 3 × 5 × 5 × 23 × 23


Again,


23805 × 5 = (3× 5 × 23) × (3 × 5 × 23)


= 345 × 345


= (345)2


Therefore, product is the square of 345


(ii) 12150


Resolving 12150 into prime factors, we get


12150 = 2 × 2 × 2 × 2 × 3 × 3 × 5 × 5 × 2


Obtained factors can be paired into equal factors except for 2


To pair it equally multiply with 2


12150 × 2 = 2 × 2 × 2 × 2 × 2 × 2 × 5 × 5 × 3 × 3


Again,


12150 × 2 = (5 × 3 × 2 × 2 × 2) × (5 × 3 × 2 × 2 × 2)


= 120 × 120


= (120)2


Therefore, product is the square of 120


(iii) 7688


Resolving 7688 into prime factors, we get


7688 = 2 × 2 × 31 × 31 × 2


Obtained factors can be paired into equal factors except for 2


To pair it equally multiply with 2


7688 × 2 = 2 × 2 × 2 × 2 × 31 × 31


Again,


7688 × 2 = (2× 2 × 31) × (2 × 2 × 31)


= 124 × 124


= (124)2


Therefore, product is the square of 124



Question 4.

Find the smallest number by which the given number must be divided so that the resulting number is a perfect square:

(i) 12283

(ii) 1800

(iii) 2904


Answer:

(i) 12283


Resolving 14283 into prime factors, we get


14283 = 3 × 3 × 3 × 23 × 23


Obtained factors can be paired into equal factors except for 3


So, eliminate 3 by diving the dividing the number with 3


= (3 × 3) × (23 × 23)


Again,


= (3 × 23) × (3 × 23)


= 69 × 69


= (69)2


Therefore,


The resultant is the square of 69


(ii) 1800


Resolving 1800 into prime factors, we get


1800 = 2 × 2 × 5 × 5 × 3 × 3 × 2


Obtained factors can be paired into equal factors except for 2


So, eliminate 2 by diving the dividing the number with 2


= (2 × 2) × (3 × 3) × (5 × 5)


Again,


= (2 × 3 × 5) × (2 × 3 × 5)


= 30 × 30


= (30)2


Therefore,


The resultant is the square of 30


(iii) 2904


Resolving 2904 into prime factors, we get


2904 = 2 × 2 × 11 × 11 × 2 × 3


Obtained factors can be paired into equal factors except for 2 and 3


So, eliminate 6 by diving the dividing the number with 6


= (2 × 2) × (11 × 11)


Again,


= (2 × 11) × (2 × 11)


= 22 × 22


= (22)2


Therefore,


The resultant is the square of 22



Question 5.

Which of the following numbers are perfect squares?

11, 12, 16, 32, 36, 50, 64, 79, 81, 111, 121


Answer:

11: Since 11 is a prime number,

Hence, it is not a perfect square


12: Since, 12 is ending with 2,


Hence, not a perfect square


16: Since, 16 = 4 × 4


= (16)2


Therefore, it is a perfect square


32: Since, 32 is ending with 2,


Hence, not a perfect square


36: Since, 36 = 62


Hence, it is a perfect square


50: Since, 50 = 52 × 2


Hence, it is not a perfect square


64: Since, 64 = 82


Hence, it is a perfect square


79: Since it is a prime number so it cannot be a perfect square


81: Since, 81 = 92


Hence, it is a perfect square


111: Since, 111 is a prime number so it cannot be a perfect square


121: Since, 121 = 112


Hence, it is perfect square



Question 6.

Using prime factorization method, find which of the following numbers are perfect squares?

189, 225, 2048, 343, 441, 2961, 11025, 3549


Answer:

Since,

189 = 32 × 3 × 7


It cannot be written as pair of two equal factors, so 189 is not a perfect square


Since,


225 = (5 × 5) × (3 × 3)


It can be written as pair of two equal factors, so 22 is a perfect square


Since,


2048 = (2 × 2) × (2 × 2) × (2 × 2) (2 × 2) × (2 × 2) × 2


All the factors cannot be written as pair of two equal factors, so 189 is not a perfect square


Since,


343 = (7 × 7) × 7


It cannot be written as pair of two equal factors, so 343 is not a perfect square


Since,


441 = (7 × 7) × (3 × 3)


It can be written as pair of two equal factors, so 441 is a perfect square


Since,


2916 = (3 × 3) × (3 × 3) × (3 × 3) × (2 × 2)


It can be written as pair of two equal factors, so 2916 is a perfect square


Since,


11025 = (5 × 5) × (3 × 3) × (7 × 7)


It can be written as pair of two equal factors, so 11025 is a perfect square


Since,


3549 = (13 × 13) × 3 × 7


It cannot be written as pair of two equal factors, so


3549 is not a perfect square



Question 7.

By what number should each of the following numbers by multiplied to get a perfect square in each case? Also find the number whose square is the new number.

(i) 8820 (ii) 3675

(iii) 605 (iv) 2880

(v) 4056 (vi) 3468

(vii) 7776


Answer:

(i) 8820


8820 = (2 × 2) × (3 × 3) × (7 × 7) × 5


In the above factors only 5 is unpaired


So, multiply the number with 5 to make it paired


Again,


8820 × 5 = 2 × 2 × 3 × 3 × 7 × 7 × 5 × 5


= (2 × 2) × (3 × 3) × (7 × 7) (5 × 5)


= (2 × 3 × 7 × 5) × (2 × 3 × 7 × 5)


= 210 × 210


= (210)2


So, the product is the square of 210


(ii) 3675


3675 = (5 × 5) × (7 × 7) × 3


In the above factors only 3 is unpaired


So, multiply the number with 3 to make it paired


Again,


3675 × 3 = 5 × 5 × 7 × 7 × 3 × 3


= (5 × 5) × (7 × 7) × (3 × 3)


= (3 × 5 × 7) × (3 × 5 × 7)


= 105 × 105


= (105)2


So, the product is the square of 105


(iii) 605


605 = 5 × (11 × 11)


In the above factors only 5 is unpaired


So, multiply the number with 5 to make it paired


Again,


605 × 5 = 5 × 5 × 11 × 11


= (5 × 5) × (11 × 11)


= (5 × 11) × (5 × 11)


= 55 × 55


= (55)2


So, the product is the square of 55


(iv) 2880


2880 = 5 × (3 × 3) × (2 × 2) × (2 × 2) × (2 × 2)


In the above factors only 5 is unpaired


So, multiply the number with 5 to make it paired


Again,


2880 × 5 = 2 × 2 × 2 × 2 × 2 × 2 × 3 × 3 × 5 × 5


= (2 × 2) × (2 × 2) × (2 × 2) (3 × 3) × (5 × 5)


= (2 × 2 × 2 × 3 × 5) × (2 × 2 × 2 × 3 × 5)


= 120 × 120


= (120)2


So, the product is the square of 120


(v) 4056


4056 = (2 × 2) × (13 × 13) × 2 × 3


In the above factors only 2 and 3 are unpaired


So, multiply the number with 6 to make it paired


Again,


4056 × 6 = 2 × 2 × 13 × 13 × 2 × 2 × 3 × 3


= (2 × 2) × (13 × 13) × (2 × 2) (3 × 3)


= (2 × 2 × 3 × 13) × (2 × 2 × 3 × 13)


= 156 × 156


= (156)2


So, the product is the square of 156


(vi) 3468


3468 = (2 × 2) × 3 × (17 × 17)


In the above factors only 3 are unpaired


So, mulityply the number with 3 to make it paired


3468 × 3 = (2 × 2) × (3 × 3) × (17 × 17)


= (2 × 3 × 17) × (2 × 3 × 17)


= 102 × 102


= (102)2


So, the product is the square of 102


(vii) 7776


7776 = (2 × 2) × (2 × 2) × (3 × 3) × (3 × 3) × 2 × 3


In the above factors only 2 and 3 are unpaired


So, multiply the number with 6 to make it paired


Again,


7776 × 6 = 2 × 2 × 2 × 2 × 2 × 2 × 3 × 3 × 3 × 3 × 3 × 3


= (2 × 2) × (2 × 2) × (2 × 2) (3 × 3) × (3 × 3) × (3 × 3)


= (2 × 2 × 2 × 3 × 3 × 3) × (2 × 2 × 2 × 3 × 3 × 3)


= 216 × 216


= (216)2


So, the product is the square of 216



Question 8.

By What numbers should each of the following be divided to get a perfect square in each case? Also, find the number whose square is the new number.

(i) 16562

(ii) 3698

(iii) 5103

(iv) 3174

(v) 1575


Answer:

(i) 16562

16562 = (7 × 7) × (13 × 13) × 2


= (7 × 7) × (13 × 13)


= (7 × 13) × (7 × 13)


= 91 × 91


= 912


Therefore, the resultant is the square of 91


(ii) 3698


3698 = 2 × (43 × 43)


= 43 × 43


= 432


Therefore, the numbers must be divided by 2 and resultant is square of 43


(iii) 5103


5103 = (3 × 3) × (3 × 3) × (3 × 3) × 7


= (3 × 3 × 3) × (3 × 3 × 3)


= 27 × 27


= 272


Therefore, the number must be divided by 7 and resultant is square of 27


(iv) 3174


3174 = 2 × 3 × (23 × 23)


= 23 × 23


= 232


Therefore, the number must be divided by 6 and the resultant is square of 23


(v) 1575


1575 = 3 × 3 × 5 × 5 × 7


= 3 × 3 × 5 × 5


= (3 × 5) × (3 × 5)


= 15 × 15


= 152


Therefore, the number must be divided by 7 and the resultant is square of 15



Question 9.

Find the greatest number of two digits which is a pefect square.


Answer:

Greatest 2 digit number = 99


Hence, greatest 2 digit perfect square number is:


99 – 18 = 81



Question 10.

Find the least number of three disgits which is perfect square.


Answer:

Smallest 3 digit number = 100

At first we will find the square root of 100



Hence, the least number that is a perfect square is 100 itself



Question 11.

Find the smallest number by which 4851 must be multiplied so that the product becomes a perfect square.


Answer:

Factors of 4851 are:

4851 = 3 × 3 × 7 × 7 × 11


Pairs = 32 × 72


Hence, 4851 should be multiplied by 11 in order to get a perfect square when smallest number multiplied to 4851



Question 12.

Find the smallest number by which 28812 must be divided so that it becomes a perfect square. Also find the number whose square is the resulting number.


Answer:

Factors of 28812 are:

28812 = 2 × 2 × 3 × 3 × 3 × 17 × 17


Pairs = 22 × 32 × 172


Hence, 28812 should be divided by 3 in order to get a perfect square when divided by the least number


The square root will be:


2 × 3 × 17 = 102




Question 13.

Find the smallest number by which 1152 must be divided so that it becomes a perfect square. Also find the number whose square is the resulting number.


Answer:

Factors of 1152 are:


1152 = 27 × 32


Pairs = 26 × 32


Hence, 1152 should be divided by 2 in order to get the perfect square.


Hence the number after division by 2 = 1152/2 = 576


Factors of 576 are = 26 × 32 = 242


Hence, resulting number is the square of 24.




Exercise 3.2
Question 1.

The following numbers are not perfect squares. Give reason.

(i) 1547 (ii) 45743

(iii)8948 (iv) 333333


Answer:

Numbers ending with 2, 3, 7 or 8 are not perfect squares. So,

(i) 1547


(ii) 45743


(iii) 8948


(iv) 333333 are not perfect squares



Question 2.

Show that the following numbers are not, perfect squares:

(i) 9327 (ii) 4058

(iii)22453 (iv) 743522


Answer:

Hence, 7, 8, 3, 2 as ending numbers respectively. As mentioned above ending with 2, 3, 7, 8 are not perfect square. So, these given numbers are not perfect squares



Question 3.

The square of which of the following numbers would be an old number?

(i) 731 (ii) 3456

(iii)5559 (iv) 42008


Answer:

Square of an odd number is an odd number

Square of an even number is an even number


(i) 731: It is an odd number so its square is also odd number


(ii) 3456: It is an even number so its square is also even number


(iii) 5559: It is an odd number so its square is also odd number


(iv) 42008: It is an even number so its square is also even number



Question 4.

What will be the units digit of the squares of the following numbers?

(i) 52 (ii) 977

(iii) 4583 (iv) 78367

(v) 52698 (vi) 99880

(vii) 12796 (viii) 55555

(ix) 53924


Answer:

(i) 52

Unit digit of (52)2 = unit digit of (2)2 = 4


(ii) 977


Unit digit of (977)2 = unit digit of (7)2 = 9


(iii) 4583


Unit digit of (4583)2 = unit digit of (3)2 = 9


(iv) 78367


Unit digit of (78367)2 = unit digit of (7)2 = 9


(v) 52698


Unit digit of (52698)2 = unit digit of (8)2 = 4


(vi) 99880


Unit digit of (99880)2 = unit digit of (0)2 = 0


(vii) 12796


Unit digit of (12796)2 = unit digit of (6)2 = 6


(viii) 55555


Unit digit of (55555)2 = unit digit of (5)2 = 5


(ix) 53924


Unit digit of (53924)2 = unit digit of (4)2 = 6



Question 5.

Observe the following pattern

And write the value of 1+3+5+7+9+……… upto n terms.


Answer:

The pattern here is the square of the number on the Right-hand side is equal to the sum of all the numbers on the left-hand side.

Thus, for n terms,

1 + 3 + 5 +…..n terms = n2 [As there are n terms]


Question 6.

Observe the following pattern



And find the value of

(i) 1002-992 (ii) 1112-1092

(iii)992-962


Answer:

(i) 1002 – 992

= 100 + 99


= 199


(ii) 1112 - 1092


= 1112 – 1102 + 1102 - 1092


= (111 + 110) + (110 + 109)


= 440


(iii) 992 - 962


= 992 – 982 + 982 – 972 + 972 - 962


= (99 + 98) + (98 + 92) + (97 + 96)


= 585



Question 7.

Which of the following triplets are Pythagorean?

(i) (8, 15, 17)

(ii) (18, 80, 82)

(iii) (14, 48, 51)

(iv) (10, 24, 26)

(v) (16, 63, 65)

(vi) (12, 35, 38)


Answer:

(i) (8, 15, 17)


L.H.S = 82 + 152 = 289


R.H.S = 172 = 289


L.H.S = R.H.S


So, it is Pythagoras


(ii) (18, 80, 82)


L.H.S = 182 + 802 = 6724


R.H.S = 822 = 6724


L.H.S = R.H.S


So, it is Pythagoras


(iii) (14, 48, 51)


L.H.S = 142 + 482 = 2500


R.H.S = 512 = 2601


L.H.S ≠ R.H.S


So, it is not Pythagoras


(iv) (10, 24, 26)


L.H.S = 102 + 242 = 676


R.H.S = 262 = 676


L.H.S = R.H.S


So, it is Pythagoras


(v) (16, 63, 65)


L.H.S = 162 + 632 = 4225


R.H.S = 652 = 4225


L.H.S = R.H.S


So, it is Pythagoras


(vi) (12, 35, 38)


L.H.S = 122 + 352 = 1369


R.H.S = 382 = 1444


L.H.S ≠ R.H.S


So, it is Pythagoras



Question 8.

Observe the following pattern


And find the value of



Answer:

From observation:

(1 × 2) + (2 × 3) + (3 × 4) + (4 × 5) + (5 × 6) =


= 70



Question 9.

Observe the following pattern

And find the values of each of the following:
(i) 1+2+3+4+5+……….+50
(ii) 31+32+……..+50


Answer:

R.H.S = [No. of terms in L.H.S × (No. of terms + 1)] (Therefore, only when L.H.S starts with 1)

Therefore,

(i) 1 + 2 + 3 +…..50 = [50 × (50 + 1)]

= 25 × 51

= 1275

(ii) 31 + 32 +…..+50 = (1 + 2 + 3 + …. + 50) – (1 + 2 + ….. 30)

= 1275 – [ (30 × 30 +1)]

= 1275 – 465

= 810


Question 10.

Observe the following pattern


And find the values of each of the following.

(i)

(ii)


Answer:

R.H.S = [(No. of terms in L.H.S) × (No. + 1) × (2 × No. + 1)]

(i) 12 + 22 + 32 + 42 + …… + 102 = [10 (10 + 1) × (2 × 10 + 1)]


= [2310]


= 385


(ii) 52 + 62 +….. + 122 = 12 + 22 + ….. 122 – (12 + 22 + 33 + 42)


= [12 × (12 + 1) × (2 × 12 + 1)] - [4 ×(4 + 1) × (2 × 4 + 1)]


= 650 – 30


= 620


Question 11.

Which of the following numbers are squares of even numbers?

121, 225, 256, 324, 1296, 6561, 5476, 4489, 373758


Answer:

Only even numbers be the square of even numbers

So, 256, 324, 1296, 5476, 373758 can be square of even numbers but 373758 is not a perfect square


So, 256, 324, 1296, 5476 are numbers



Question 12.

By just examining the units digits, can you tell which of the following cannot be whole squares?

(i) 1026 (ii) 1028

(iii)1024 (iv) 1022

(v) 1023 (vi) 1027


Answer:

Numbers ending with 2, 3, 7, 8 cannot be perfect square. So,

1028 (iv) 1022 (v) 1023 (vi) 1027 cannot be whole squares.



Question 13.

Which of the numbers for which you cannot decide whether they are squares.


Answer:

All the natural numbers whose unit digit is 0, 1, 4, 5, 6 or 9 can not be said surely if they are square numbers or not



Question 14.

Write five numbers which you cannot decide whether they are square just by looking at the unit’s digit.


Answer:

Any natural number ending with 0, 1, 4, 5, 6 or 9 can be or cannot be a square number.

Hence,


The five examples are:


(i) 2061


The ending digit is 1. Hence, it may or may not be a square number


(ii) 1069


The ending digit is 9. Hence, it may or may not be a square number


(iii) 1234


The ending digit is 4. Hence, it may or may not be a square number


(iv) 56790


The ending digit is 0. Hence, it may or may not be a square number


(v) 76555


The ending digit is 5. Hence, it may or may not be a square number



Question 15.

Write true (T) or false (F) for the following statements.

(i) The number of digits in a square number is even.

(ii) The square of a prime number is prime

(iii) The sum of two square numbers is a square number.

(iv) The difference of two square numbers is a square number.

(v) The product of two square numbers is a square number.

(vi) No square number is negative.

(vii) There is no square number between 50 and 56.

(viii) There are fourteen square number upto 200.


Answer:

(i) False: Because 169 is square number with odd digit

(ii) False: Square of 3 (Prime) is 9 (not prime)


(iii) False: Sum of 22 and 32 is 13 which is not square number


(iv) False: Difference of 32 and 22 is 5, which is not square number


(v) True: Because the square of 22 and 32 is 36 which is square of 6


(vi) True: As (-2)2 is 4, i.e. not negative


(vii) True: As there is no square number between them


(viii) True: The fourteen numbers upto 200 are: 1, 4, 9, 16, 25, 36, 49, 64, 81, 100, 121, 144, 169, 196




Exercise 3.3
Question 1.

Find the squares of the following numbers using column method. Verify the result by finding the square using the usual multiplication:

(i) 25

(ii) 37

(iii) 54

(iv) 71

(v) 96


Answer:

(i) 25

Here, a = 2, b = 5



252 = 625


And,


252 = 25× 25 = 625


(ii) 37


Here, a = 3, b = 7



372 = 1369


And,


372 = 37× 37 = 1369


(iii) 54


Here, a = 5, b = 4



542 = 2916


And,


542 = 54× 54 = 2916


(iv) 71


Here, a = 7, b = 1



712 = 4941


And,


712 = 71× 71 = 4941


(v) 96


Here, a = 9, b = 6



962 = 9216


And,


962 = 96× 96 = 9216



Question 2.

Find the squares of the following numbers using diagonal method:

(i) 98

(ii) 273

(iii)348

(iv) 295

(v) 171


Answer:

(i) 98

Step I: Obtain the number and count the number of digits in it. Let there be n digits in the number to be squared.


Step II: Draw square and divide it into n2 sub-squares of the same size by drawing (n - 1) horizontal and (n - 1) vertical lines.


Step III: Draw the diagonals of each sub-square.


Step IV: Write the digits of the number to be squared along left vertical side sand top horizontal side of the squares as shown below.


Step V: Multiply each digit on the left of the square with each digit on top of the column one-by-one. Write the units digit of the product below the diagonal and tens digit above the diagonal of the corresponding sub-square.


Step VI: Starting below the lowest diagonal sum the digits along the diagonals so obtained. Write the units digit of the sum and take carry, the tens digit (if any) to the diagonal above.


Step VII: Obtain the required square by writing the digits from the left-most side.


(98)2 = 9604


(ii) 273


Step I: Obtain the number and count the number of digits in it. Let there be n digits in the number to be squared.


Step II: Draw square and divide it into n2 sub-squares of the same size by drawing (n - 1) horizontal and (n - 1) vertical lines.


Step III: Draw the diagonals of each sub-square.


Step IV: Write the digits of the number to be squared along left vertical side sand top horizontal side of the squares as shown below.


Step V: Multiply each digit on the left of the square with each digit on top of the column one-by-one. Write the units digit of the product below the diagonal and tens digit above the diagonal of the corresponding sub-square.


Step VI: Starting below the lowest diagonal sum the digits along the diagonals so obtained. Write the units digit of the sum and take carry, the tens digit (if any) to the diagonal above.


Step VII: Obtain the required square by writing the digits from the left-most side.


(273)2= 74529


(iii)348


Step I: Obtain the number and count the number of digits in it. Let there be n digits in the number to be squared.


Step II: Draw square and divide it into n2 sub-squares of the same size by drawing (n - 1) horizontal and (n - 1) vertical lines.


Step III: Draw the diagonals of each sub-square.


Step IV: Write the digits of the number to be squared along left vertical side sand top horizontal side of the squares as shown below.


Step V: Multiply each digit on the left of the square with each digit on top of the column one-by-one. Write the units digit of the product below the diagonal and tens digit above the diagonal of the corresponding sub-square.


Step VI: Starting below the lowest diagonal sum the digits along the diagonals so obtained. Write the units digit of the sum and take carry, the tens digit (if any) to the diagonal above.


Step VII: Obtain the required square by writing the digits from the left-most side.



3482 = 121104


(iv) 295


Step I: Obtain the number and count the number of digits in it. Let there be n digits in the number to be squared.


Step II: Draw square and divide it into n2 sub-squares of the same size by drawing (n - 1) horizontal and (n - 1) vertical lines.


Step III: Draw the diagonals of each sub-square.


Step IV: Write the digits of the number to be squared along left vertical side sand top horizontal side of the squares as shown below.


Step V: Multiply each digit on the left of the square with each digit on top of the column one-by-one. Write the units digit of the product below the diagonal and tens digit above the diagonal of the corresponding sub-square.


Step VI: Starting below the lowest diagonal sum the digits along the diagonals so obtained. Write the units digit of the sum and take carry, the tens digit (if any) to the diagonal above.


Step VII: Obtain the required square by writing the digits from the left-most side.


(295)2 = 87025


(v) 171


Step I: Obtain the number and count the number of digits in it. Let there be n digits in the number to be squared.


Step II: Draw square and divide it into n2 sub-squares of the same size by drawing (n - 1) horizontal and (n - 1) vertical lines.


Step III: Draw the diagonals of each sub-square.


Step IV: Write the digits of the number to be squared along left vertical side sand top horizontal side of the squares as shown below.


Step V: Multiply each digit on the left of the square with each digit on top of the column one-by-one. Write the units digit of the product below the diagonal and tens digit above the diagonal of the corresponding sub-square.


Step VI: Starting below the lowest diagonal sum the digits along the diagonals so obtained. Write the units digit of the sum and take carry, the tens digit (if any) to the diagonal above.


Step VII: Obtain the required square by writing the digits from the left-most side.


(171)2 = 29241



Question 3.

Find the squares of the following numbers:

(i) 127 (ii) 503

(iii) 450 (iv) 862

(v) 265


Answer:

(i) (127)2 = 127 × 127

= 16129


(ii) (503)2 = 503 × 503


= 253009


(iii) (451)2 = 451 × 451


= 203401


(iv) (862)2 = 862 × 862


= 743044


(v) (265)2 = 265 × 265


= 70225



Question 4.

Find the squares of the following numbers:

(i) 425 (ii) 575

(iii)405 (iv) 205

(v) 95 (vi) 745

(vii) 512 (viii) 995


Answer:

(i) 425


We know that,


The square of 425 is:


(425)2 = 425 × 425


= 180625


Hence, the square of 425 is 180625


(ii) 575


We know that,


The square of 575 is:


(575)2 = 575 × 575


= 330625


Hence, the square of 575 is 330625


(iii) 405


We know that,


The square of 405 is:


(405)2 = 405 × 405


= 164025


Hence, the square of 405 is 164025


(iv) 205


We know that,


The square of 205 is:


(205)2 = 205 × 205


= 42025


Hence, the square of 205 is 42025


(v) 95


We know that,


The square of 95 is:


(95)2 = 95 × 95


= 9025


Hence, the square of 95 is 9025


(vi) 745


We know that,


The square of 745 is:


(745)2 = 745 × 745


= 555025


Hence, the square of 745 is 555025


(vii) 512


We know that,


The square of 512 is:


(512)2 = 512 × 512


= 262144


Hence, the square of 512 is 262144


(viii) 995


We know that,


The square of 995 is:


(995)2 = 995 × 995


= 990025


Hence, the square of 995 is 990025



Question 5.

Find the squares of the following numbers using the identify :

(i) 405

(ii) 510

(iii) 1001

(iv) 209

(v) 605


Answer:

(i) 405

We have,


(405)2 = (400 + 5)2


= (400)2 + 52 + 2 (400) (5)


= 160000 + 25 + 4000


= 164025


(ii) 510


We have,


(510)2 = (500 + 10)2


= 250000 + 100 + 10000


= 260100


(iii) 1001


We have,


(1001)2 = (1000 + 1)2


= (1000)2 + 1 + 2 (1000)


= 1000000 + 1 + 2000


= 1002001


(iv) 209


We have,


(209)2 = (200 + 9)2


= (200)2 + 92 + 2 (200) (9)


= 40000 + 81 + 3600


= 43681


(v) 605


We have,


(605)2 = (600 + 5)2


= (600)2 + 52 + 2 (600) (5)


= 360000 + 25 + 6000


= 366025



Question 6.

Find the squares of the following numbers using the identity

(i) 395 (ii) 995

(iii)495 (iv) 498

(v) 99 (vi) 999

(vii)599


Answer:

(i) 395


395 = (400 – 5)2


= (400)2 + 52 – 2 (400) (5)


= 160000 + 25 – 4000


= 156025


(ii) 995


995 = (1000 – 5)2


= (1000)2 + 52 – 2 (1000) (5)


= 1000000 + 25 – 10000


= 990025


(iii)495


495 = (500 – 5)2


= (500)2 + 52 – 2 (500) (5)


= 250000 + 25 – 5000


= 245025


(iv) 498


498 = (500 – 2)2


= (500)2 + 22 – 2 (500) (2)


= 250000 + 4 – 2000


= 248004


(v) 99


99 = (100 – 1)2


= (100)2 + 12 – 2 (100) (1)


= 10000 + 1 – 200


= 9799


(vi) 999


999 = (1000 – 1)2


= (1000)2 + 12 – 2 (1000) (1)


= 1000000 + 1 – 2000


= 998001


(vii)599


(600 – 1)2


= (600)2 + 12 – 2 (600) (1)


= 360000 + 1 – 1200


= 358801



Question 7.

Find the squares of the following numbers by visual method:

(i) 52 (ii) 95

(iii) 505 (iv) 702

(v) 99


Answer:

(i) 52, (52)2 = (50 + 2)2

= 502 + 22 + (2 × 50 × 2)


= 2500 + 4 + 200


= 2704


(ii) 95, (95)2 = (100 - 5)2


= 1002 + 52 - (2 × 5 × 100)


= 10000 + 25 - 1000


= 9025


(iii) 505, (505)2 = (505 + 5)2


= 5002 + 52 + (2 × 500 × 5)


= 250000 + 25 + 5000


= 255025


(iv) 702, (702)2 = (700 + 2)2


= 7002 + 22 + (2 × 700 × 2)


= 140000 + 4 + 2800


= 142804


(v) 99, (99)2 = (100 - 1)2


= 1002 + 12 - (2 × 100 × 1)


= 10000 + 1 - 200


= 9301




Exercise 3.4
Question 1.

Write the possible unit’s digits of the square root of the following numbers. Which of these numbers are odd square roots?

(i) 9801

(ii) 99856

(iii) 998001

(iv) 657666025


Answer:

(i) 9801

Unit digit = 1


Unit digit of square root = 1 or 9


As number is odd, square root is also odd


(ii) 99856


Unit digit = 6


Unit digit of square root = 4 or 6


As number is even, square root is also even


(iii) 998001


Unit digit = 1


Unit digit of square root = 1 or 9


As number is odd, square root is also odd


(iv) 657666025


Unit digit = 5


Unit digit of square root = 5


As number is odd, square root is also odd



Question 2.

Find the square root of each of the following by prime factorization.

(i) 441 (ii) 196

(iii) 529 (iv) 1764

(v) 1156 (vi) 4096

(vii) 7056 (viii) 8281

(ix) 11664 (x) 47089

(xi) 24336 (xii) 190969

(xiii) 586756 (xiv) 27225

(xv) 3013696


Answer:

(i) 441

441 = 32 × 72


= 3 × 7


= 21



(ii) 196


196 = 22 × 72


= 2 × 7


= 14



(iii) 529


529 = 232


= 23



(iv) 1764


1764 = 22 × 32 × 72


= 2 × 3 × 7


= 42



(v) 1156


1156 = 22 × 172


= 2 × 17


= 34



(vi) 4096


4096 = 212


= 26


= 64



(vii) 7056


7056 = 22 × 22 × 212


= 2 × 2 × 21


= 84



(viii) 8281


8281 = 912


= 91



(ix) 11664


11664 = 22 × 22 × 32 × 32 × 32


= 2 × 2 × 3 × 3× 3


= 108



(x) 47089


47089 = 2172


= 217


(xi) 24336


24336 = 22 × 22 × 32 × 132


= 2 × 2 × 3 × 13


= 156



(xii) 190969


190969 = 232 × 192


= 23 × 19


= 437



(xiii) 586756


586756 = 22 × 3832


= 2 × 383


= 766


(xiv) 27225


27225 = 52 × 32 × 112


= 5 × 3 × 11


= 165


(xv) 3013696


3013696 = 26 × 2172


= 23 × 217


= 1736




Question 3.

Find the smallest number by which 180 must be multiplied so that it becames a perfect square. Also, find the square root of the perfect square so obtained.


Answer:

180 = 22 × 32 × 5

= (2 × 2) × (3 × 3) × 5


To make the unpaired 5 into paired, multiply the number with 5


Therefore,


180 × 5 = 22 × 32 × 52


Hence, square root of number = × = 2 × 3 × 5


= 30



Question 4.

Find the smallest number by which 147 must be multiplied so that it becomes a perfect square. Also, find the square root of the number so obtained.


Answer:

147 = 72 × 3

To make the unpaired 3 into paired, multiply the number with 3


Therefore,


147 × 3 = 72 × 32


Hence, square root of number = √147 × √3 = 7 × 3


= 21


Question 5.

Find the smallest number by which 3645 must be divided so that it becomes a perfect square. Also, find the square root of the resulting number.


Answer:

3645 = 5 × (3 × 3) × (3 × 3) × 3

Here 5 and 3 are unpaired so we have to divide 3645 with 5 × 3 = 15


Therefore,


= 32 × 32


Hence,


Square root of numbers = = 3 × 3


= 9



Question 6.

Find the smallest number by which 1152 must be divided so that it becomes a square. Also, find the square root of the number so obtained.


Answer:

1152 = (2 × 2) × (2 × 2) × 2 × (3 × 3)

Here 2 is unpaired so we have to divide 1152 with 2


Therefore,


= 22 × 22 × 22 × 32


Hence,


Square root of numbers = = 2 × 2 × 2 × 3


= 24



Question 7.

The product of two numbers is 1296. If one number is 16 times the other, find the numbers.


Answer:

Let a and b be two numbers

a × b = 1296


a = 16b


= 16 b × b


= 1296


b2 = 81


b = 9


Therefore,


a = 144 and b = 9



Question 8.

A welfare association collected Rs 202500 as donation from the residents. If each paid as many rupees as there were residents, find the number of residents.


Answer:

Let total residents be a

Therefore, each paid Rs. a

Total collection = a (a) = a2

given, Total Collection = 202500

Hence,

a =
a = √(2 × 2 × 3 × 3 × 3 × 3 × 5 × 5 × 5 × 5)
a = 2 × 3 × 3 × 5 × 5
a = 450

Therefore,

Total residents = 450


Question 9.

A society collected Rs 92.16. Each member collected as many paise as there were members. How many members were there and how much did each contribute?


Answer:

Let there were a members

Therefore, each attributed a paise


Therefore,


a (a), i.e. total cost collected = 9216 paise


a2 = 9216


a =


= 2 × 2 × 2 × 12


= 96


Therefore, there were 96 members and each contributed 96 paise



Question 10.

A society collected Rs 2304 as fees from its students. If each student paid as many paise as there were students in the school, how many students were there in the school?


Answer:

Let, a be number of school students

Therefore, each student contributed a paise


Total money obtained = a2paise


= 230400 paise


a =


=


= 10


a = 10 × 2 × 2 × 12


a = 480


Therefore, there were 480 students



Question 11.

The area of a square field is 5184 m2. A rectangular field, whose length is twice its breadth has its perimeter equal to the perimeter of the square field. Find the area of the rectangular field.


Answer:

Let ‘a’ be the side of square field

Therefore,


a2 = 5184 m2


a = m


a = 2 × 2 ×2 × 9


= 72 m


Perimeter of square = 4a


= 288 m


Perimeter of rectangle = 2 (l + b)


= 288 m


2 (2b + b) = 288


b = 48 and l = 96


Area of rectangle = 96 × 48 m2


= 4608 m2



Question 12.

Find the least square number, exactly divisible by each one of the numbers: (i) 6,9, 15 and 20) (ii) 8,12, 15 and 20


Answer:

(i) 6, 9, 15 and 20

L.C.M of given 4 numbers is 180


180 = 22 × 32 × 5


To make it a perfect square, we have to multiply the number with 5


Therefore,


180 × 5 = 22 × 32 × 52


900 is the least square number divisible by 6, 9, 15 and 20


3600 is the least square number divisible by 8, 12, 15 and 20


(ii) 8, 2, 15 and 20


L.C.M of given 4 numbers is 360


360 = 22 × 32 ×2 × 5


To make it a perfect square, we have to multiply the number with 2 × 5 = 10


Therefore,


360 × 10 = 22 × 32 × 52 × 22



Question 13.

Find the square roots of 121 and 169 by the method of repeated subtraction.


Answer:

121 – 1 = 120

120 – 3 = 117


117 – 5 = 112


112 – 7 = 115


115 – 9 = 106


106 – 11 = 95


95 – 13 = 82


82 – 15 = 67


67 – 17 = 50


50 – 19 = 31


31 – 21 = 10


Clearly, we have performed operation 11 times


Therefore,


= 11



168 – 3 = 165


165 – 5 = 160


160 – 7 = 153


153 – 9 = 144


144 – 11 = 133


133 – 13 = 120


120 – 15 = 105


105 – 17 = 88


88 – 19 = 69


69 – 21 = 48


48 – 23 = 25


25 – 25 = 0


Clearly, we have performed subtraction 13 times


Therefore,


= 13



Question 14.

Write the prime factorization of the following numbers and hence find their square roots.

(i) 7744

(ii) 9604

(iii) 5929

(iv) 7056


Answer:

(i) 7744

7744 = 22 × 22 × 22 × 112


= 2 × 2× 2 × 11


=88


(ii) 9604


9604 = 22 × 72 × 72


= 2 × 7× 7


=


(iii) 5929


5929 = 112 × 72


= 11 × 7


=77


(iv) 7056


7056 = 22 × 22 × 72 × 32


= 2 × 2× 7 × 3


=84



Question 15.

The students of class VIII of a school donated Rs 2401 for PM’s National Relief Fund. Each student donated as many rupees as the number of students in the class, Find the number of students in the class.


Answer:

Let a be the number of students

Therefore,


Each student denoted a rupee


So,


Total amount collected = a × a rupees


= 2401


a2 = 2401


a = 49


Therefore,


There are 49 students in the class



Question 16.

A PT teacher wants to arrange maximum possible number of 6000 students in a field such that the number of rows is equal to the number of columns. Find the number of rows if 71 were left out after arrangement.


Answer:

Let a be number of rows

Therefore,


No. of columns = a


Total number of students who sat in field = a2


Total students = a2 + 71


= 6000


a2 = 5929


a =


a = 11 × 7


= 77


Therefore, total number of rows = 77




Exercise 3.5
Question 1.

Find the square root of each of the following by long division method:

(i) 12544 (ii) 97344

(iii) 286225 (iv) 390625

(v) 363609 (vi) 974169

(vii) 120409 (viiii) 1471369

(ix) 291600 (x) 9653449

(xi) 1745041 (xii) 4008004

(xiii) 20657025 (xiv) 152547201

(xv) 20421361 (xvi)62504836

(xvii) 82264900 (xviii) 3226694416

(xix) 6407522209 (xx) 3915380329


Answer:

(i) 12544


Therefore,


= 112


(ii) 97344



Therefore,


= 312


(iii) 286225



Therefore,


= 535


(iv) 390625



= 625


(v) 363609



Therefore,


= 603


(vi) 974169



Therefore,


= 987


(vii) 120409



Therefore,


= 347


(viiii) 1471369



Therefore,


= 1213


(ix) 291600



Therefore,


= 540


(x) 9653449



Therefore,


= 3107


(xi) 1745041



Therefore,


= 1321


(xii) 4008004



Therefore,


= 2002


(xiii) 20657025



= 4545


(xiv) 152547201



Therefore,


= 12351


(xv) 20421361



Therefore,


= 4519


(xvi) 62504836



Therefore,


= 7906


(xvii) 82264900



Therefore,


= 9070


(xviii) 3226694416



= 56804


(xix) 6407522209



Therefore,


= 80047


(xx) 3915380329





Question 2.

Find the least number which must be subtracted from the following numbers to make them a perfect square:

(i) 2361

(ii) 194491

(iii) 26535

(iv) 161605

(v) 4401624


Answer:

(i) 2361


Hence,


57 must be subtracted from 2361 in order to get a perfect square



(ii) 194491


Hence,


10 must be subtracted from 194491 in order to get a perfect square



(iii) 26535


Hence,


291 must be subtracted from 26535 in order to get a perfect square



(iv) 161605


Hence,


1 must be subtracted from 161605 in order to get a perfect square



(v) 4401624


Hence,


20 must be subtracted from 4401624 in order to get a perfect square number




Question 3.

Find the least number which must be added to the following numbers to make them a perfect square:

(i) 5607

(ii)4931

(iii) 4515600

(iv) 37460

(v) 506900


Answer:

(i) 5607



The remainder is 131


Hence, (74)2 < 5607


The next perfect square number is:


(75)2 = 5625 > 5607


Hence, the number to be added = 5625 – 5607


= 18


(ii)4931



The remainder is 31


Hence, (70)2 < 4931


The next perfect square number is:


(71)2 = 5041 > 4931


Hence, the number to be added = 5041 – 4931


= 110


(iii) 4515600



The remainder is 4224


Hence, (2124)2 < 4515600


The next perfect square number is:


(2125)2 = 4515625 > 4515600


Hence, the number to be added = 4515625 – 4515600


= 25


(iv) 37460



The remainder is 211


Hence, (193)2 < 37460


The next perfect square number is:


(194)2 = 37636 > 37460


Hence, the number to be added = 37636 – 37460


= 176


(v) 506900



The remainder is 1379


Hence, (711)2 < 506900


The next perfect square number is:


(712)2 = 506944 > 506900


Hence, the number to be added = 506944 – 506900


= 44



Question 4.

Find the greatest number of 5 digits which is a perfect square.


Answer:

We know that,

Greatest 5 digit number = 99999



The remainder is 143


Therefore,


The greatest 5 digit perfect square number is:


99999 – 143


= 99856


Hence, 99856 is the required greatest 5 digit perfect square number



Question 5.

Find the least number of 4 digits which is a perfect square.


Answer:

We know that,

Least 4 digit number = 1000



The remainder is 39


Therefore,


(31)2 < 1000


Hence,


The next perfect square number is:


(32)2 = 1024 > 1000


Hence, 1024 is the required number



Question 6.

Find the least number of six digits which is a perfect square.


Answer:

We know that,

Least 6 digit number = 100000



The remainder is 144


Therefore,


(316)2 < 100000


Hence, the next perfect square


(317)2 = 100489 > 100000


Hence, 100489 is the required number



Question 7.

Find the greatest number of 4 digits which is a perfect square.


Answer:

We know that,

Greatest 4 digit number = 9999



The remainder is 198


Hence,


The greatest 4 digit perfect square number = 9999 – 198


= 9801



Question 8.

A General arranges his soldiers in rows to form a perfect square. He finds that in doing so, 60 soldiers are left out. If the total number of soldiers be 8160, find the number of soldiers in each row.


Answer:

Total number of soldiers = 8160

Number of soldiers left out = 60


Number of soldiers arranged in rows to form a perfect square = 8160 – 60


= 8100


Hence, number of soldiers in each row =


=


= 90



Question 9.

The area of a square field is 60025m2. A man cycles along its boundary at 18 Km/hr. In how much time will he return at the starting point?


Answer:

Area of square field = 60025 m2

Speed of cyclist = 18 km/h


= 18 ×


= 5 m/s2


Area = 60025 m2


Side2 = 60025


Side =


= 245


Therefore,


Total length of boundary = 4 × Side


= 4 × 245


= 980 m


Hence,


Time taken =


= 196 seconds


= 3 minutes and 16 seconds



Question 10.

The cost of leveling and turning a square lawn at Rs 2.50 per m2 is Rs13322.50 Find the cost of fencing it at Rs 5 per metre.


Answer:

Rate of leveling and turning a square lawn = 2.50 per m2

Total cost of leveling and turning = Rs. 13322.50


Total area of square lawn =


= 5329 m2


Side of square lawn =


= 73 m


Total length of lawn = 4 × 73


= 292 m


Cost of fencing the lawn at Rs 5 per metre = 292 × 5


= Rs. 1460



Question 11.

Find the greatest number of three digits which is a perfect square.


Answer:

We know that,

Largest 3 digit number = 999



The remainder is 38


Hence,


The greatest 3-digit perfect square number = 999 – 38


= 961



Question 12.

Find the smallest number which must be added to 2300 so that it becomes a perfect square.


Answer:

At first we have to find,

The square root of 2300


So, the square root of 2300 is:



The remainder is 91


Hence,


(47)2 < 2300


Now, the next perfect square number is (48)2 = 2304 > 2300


Hence,


The smallest number that must be added to 2300 to get a perfect square is:


2304 – 2300


= 4




Exercise 3.6
Question 1.

Find the square root of:

(i) (ii)

(iii) (iv)

(v) (vi)

(vii) (viii)

(ix) (x)

(xi) (xii)

(xiii) (xiv)

(xv)


Answer:

(i)



(ii)



(iii)


=


(iv)


=


(v)


=


(vi)


=


(vii)


=


(viii)


=


(ix)


=


(x)


=


(xi)


=


(xii)


=


(xiii)


=


(xiv)


=


(xv)


=



Question 2.

Find the value of:

(i)

(ii)

(iii)

(iv)

(v)


Answer:

(i) = (Cancelling numerator and denominator with 5)

= (Therefore, = 4, = 9)


(ii)


= = (Therefore, = 21, = 25)


(iii) = (Cancelling numerator and denominator with 3)


= (Therefore, = 23, = 24)


(iv)


= ×


We know that,


× =


= 22 × 3 × 13


= 156


(v)


= ×


We know that,


× =


= 5 × 9 × 2


= 90



Question 3.

The area of a square field is square metres. Find the length of each side of the field.


Answer:

Given area = 80 × m2

= m2


If L is length of each side


Therefore,


L2 =


L = (Therefore, = )


=



Question 4.

The area of a square field is . Calculate the length of the side of the square.


Answer:

Given, area = 30 × m2

= m2


If L is length of each side then,


L2 =


L = =


= (Therefore, )


Therefore, length is



Question 5.

Find the length of a side of a square playground whose area is equal to the area of a rectangular field of dimensions 72m and 338 m.


Answer:

Area of rectangular field = l × b

= 72 × 338 m2


= 24336 m2


Area of square = L2 = 24336 m2


L =


= 156 m


Therefore, 156 m is the length of side of square playground.




Exercise 3.7
Question 1.

Find the square root of the following numbers in decimal form:

84.8241


Answer:

84.8241


Therefore,


√84.8241 = 9.21



Question 2.

Find the square root of the following numbers in decimal form:

0.7225


Answer:

0.7225


√0.7225 = 0.85



Question 3.

Find the square root of the following numbers in decimal form:

0.813604


Answer:

0.81304


= 0.902



Question 4.

Find the square root of the following numbers in decimal form:

0.00002025


Answer:

0.00002025




Question 5.

Find the square root of the following numbers in decimal form:

150.0625


Answer:

150.0625


= 12.25



Question 6.

Find the square root of the following numbers in decimal form:

225.6004


Answer:

225.6004


= 15.02



Question 7.

Find the square root of the following numbers in decimal form:

3600.720036


Answer:

3600.720036


= 60.006



Question 8.

Find the square root of the following numbers in decimal form:

236.144489


Answer:

236.144689


= 15.367



Question 9.

Find the square root of the following numbers in decimal form:

0.00059049


Answer:

0.00059049


= 0.0243



Question 10.

Find the square root of the following numbers in decimal form:

176.252176


Answer:

176.252176


= 13.276



Question 11.

Find the square root of the following numbers in decimal form:

9998.0001


Answer:

9998.0001


= 99.99



Question 12.

Find the square root of the following numbers in decimal form:

0.00038809


Answer:

0.00038809


= 0.0197



Question 13.

What is that fraction which when multiplied by itself gives 227.798649?


Answer:

a =



Question 14.

The area of a square playground is 256.6404 square meter. Find the length of one side of the playground.


Answer:

Given: area = L2 = 256.6 m2

L =




Question 15.

What is the fraction which when multiplied by it self gives 0.00053361?


Answer:

a2 = 0.00053361


Therefore,


a = 0.0231



Question 16.

Simplify:

(i)

(ii)


Answer:

(i)

At first, we find


Therefore,



=


= = 7.7


And,



=


= = 2.3


Now,


= 0.54


(ii)


At first, we find


Therefore,



=


= = 0.44


And,



=


= = 0.42


Now,


= 15



Question 17.

Evaluate and hence find the value of


Answer:

=


Now,



=


= = 22.5



=


= = 2.25


+


= 22.5 + 2.25


= 24.75



Question 18.

Find the value of and hence find the value of

(i)

(ii)


Answer:

=


Now,


(i)

v


= 10 × 10.15


(ii) =


= 1.015



Exercise 3.8
Question 1.

Find the square root of each of the following correct to three places of decimal.

(i) 5 (ii) 7

(iii) 17 (iv) 20

(v) 66 (vi) 427

(vii) 1.7 (viii) 23.1

(ix) 2.5 (x) 237.615

(xi) 15.3215 (xii) 0.9

(xiii) 0.1 (xiv) 0.016

(xv) 0.00064 (xvi) 0.019

(xvii) (xviii)

(xix) (xx)


Answer:

(i) 5 = 2.236


= 2.236


(ii) 7 = 2.647



= 2.646


(iii) 17 = 4.123



= 4.123


(iv) 20 = 4.472



= 4.472


(v) 66 = 8.124



= 8.124


(vi) 427 = 20.664



= 20.664


(vii) 1.7 = 1.304



= 1.304


(viii) 23.1 = 4.806



= 4.806


(ix) 2.5 = 1.581



= 1.581


(x) 237.615 = 15.415



= 15.415


(xi) 15.3215 = 3.914



= 3.914


(xii) 0.9 = 0.949



= 0.949


(xiii) 0.1 = 0.316



= 0.316


(xiv) 0.016 = 0.126



(xv) 0.00064 = 0.025



(xvi) 0.019 = 0.138



= 0.138


(xvii) = 0.875



= 0.875


(xviii) = 0.416



= 0.645


(xix) = 2.500000



(xx) = 287.62



Hence,



Question 2.

Find the square root of 12.0068 correct to four decimal places.


Answer:

The square root of 12.0068 is:


Hence,


Hence,


= 3.4651 approx



Question 3.

Find the square root of 11 correct to five decimal places.


Answer:

The square root of 11 is:


Hence,


= 3.31662



Question 4.

Give that: evaluate each of the following:

(i)

(ii)


Answer:

(i) =

=


= 4.535


(ii) =


=


=


= 28.867



Question 5.

Given that and find the square roots of the following:

(i)

(ii)

(iii)

(iv)

(v)


Answer:

(i)


=


=


=


=


=


= 1.50


(ii)


=


=


=


=


=


= 2.519


(iii)


=


=


=


=


=


= 4.627


(iv)


=


=


=


=


= 7.155


(v)


=


=


=


=


= 0.735




Exercise 3.9
Question 1.

Using square root table, find the square roots of the following:

7


Answer:

From square root table,

Square root of 7 is:


= 2.645


Therefore,


The square root of 7 is 2.645



Question 2.

Using square root table, find the square roots of the following:

15


Answer:

From square root table,

Square root of 15 is:


= 3.872


Therefore,


The square root of 15 is 3.872



Question 3.

Using square root table, find the square roots of the following:

74


Answer:

From square root table,

Square root of 74 is:


= 8.602


Therefore,


The square root of 74 is 8.602



Question 4.

Using square root table, find the square roots of the following:

82


Answer:

From square root table,

Square root of 82 is:


= 9.055


Therefore,


The square root of 82 is 9.055



Question 5.

Using square root table, find the square roots of the following:

198


Answer:

From square root table,

Square root of 198 is:


= 14.071


Therefore,


The square root of 198 is 14.071



Question 6.

Using square root table, find the square roots of the following:

540


Answer:

From square root table,

Square root of 540 is:


= 23.237


Therefore,


The square root of 540 is 23.237



Question 7.

Using square root table, find the square roots of the following:

8700


Answer:

From square root table,

Square root of 8700 is:


= 93.237


Therefore,


The square root of 8700 is 93.237



Question 8.

Using square root table, find the square roots of the following:

3509


Answer:

From square root table,

Square root of 3509 is:


= 59.236


Therefore,


The square root of 3509 is 59.236



Question 9.

Using square root table, find the square roots of the following:

6929


Answer:

From square root table,

Square root of 6929 is:


= 83.240


Therefore,


The square root of 6929 is 83.240



Question 10.

Using square root table, find the square roots of the following:

25720


Answer:

From square root table,

Square root of 25720 is:


= 160.374


Therefore,


The square root of 25720 is 160.374



Question 11.

Using square root table, find the square roots of the following:

1312


Answer:

From square root table,

Square root of 1312 is:


= 36.221


Therefore,


The square root of 1312 is 36.221



Question 12.

Using square root table, find the square roots of the following:

4192


Answer:

From square root table,

Square root of 4192 is:


= 64.745


Therefore,


The square root of 4192 is 64.745



Question 13.

Using square root table, find the square roots of the following:

49555


Answer:

From square root table,

Square root of 49555 is:


= 222.609


Therefore,


The square root of 49555 is 222.609



Question 14.

Using square root table, find the square roots of the following:



Answer:

From square root table,

Square root of is:


= 0.829


Therefore,


The square root of is 0.829



Question 15.

Using square root table, find the square roots of the following:



Answer:

From square root table,

Square root of is:


= 0.580


Therefore,


The square root of is 0.580



Question 16.

Using square root table, find the square roots of the following:



Answer:

From square root table,

Square root of is:


= 0.773


Therefore,


The square root of is 0.773



Question 17.

Using square root table, find the square roots of the following:

13.21


Answer:

From square root table,

Square root of 13.21 is:


= 3.634


Therefore,


The square root of 13.21 is 3.634



Question 18.

Using square root table, find the square roots of the following:

21.97


Answer:

From square root table,

Square root of 21.97 is:


= 4.687


Therefore,


The square root of 21.97 is 4.687



Question 19.

Using square root table, find the square roots of the following:

110


Answer:

From square root table,

Square root of 110 is:


= 10.488


Therefore,


The square root of 110 is 10.488



Question 20.

Using square root table, find the square roots of the following:

1110


Answer:

From square root table,

Square root of 1110 is:


= 33.316


Therefore,


The square root of 1110 is 33.316



Question 21.

Using square root table, find the square roots of the following:

11.11


Answer:

From square root table,

Square root of 11.11 is:


= 3.333


Therefore,


The square root of 11.11 is 3.333



Question 22.

The area of a square field is 325m2. Find the approximate length of one side of the field.


Answer:

Area of the field = 325 m2

In order to find approximate length of the side of the field we will have to calculate the square root of 325


= 18.027 m


Hence,


The approximate length of one side of the field is 18.027 m



Question 23.

Find the length of a side of a square, whose area is equal to the area of a rectangle with sides 240 m and 70 m.


Answer:

According to the question,

Area of square = Area of rectangle


Side2 = 240 × 70


Side =


=


= 20


= 20 × 6.48


= 129.60 m