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Rational Numbers

Class 8th Mathematics RS Aggarwal Solution
Exercise 1a
  1. Express -3/5 as a rational number with denominator (i) 20 (ii) -30 (iii) 35 (iv)…
  2. Express -42/98 as a rational number with denominator 7.
  3. Express -48/60 as a rational number with denominator 5.
  4. Express each of the following rational numbers in standard form: (i) -12/30 (ii)…
  5. (i) 3/8 or 0 (ii) -2/9 or 0 (iii) -3/4 or 1/4 (iv) -5/7 or -4/7 (v) 2/3 or 3/4…
  6. (i) -4/3 or -8/7 (ii) 7/-9 or -5/8 (iii) -1/3 or 4/-5 (iv) 9/-13 or 7/-12 (v)…
  7. Fill in the blanks with the correct symbol out of , = and : (i) 6/-13 6/-13 (ii)…
  8. Arrange the following rational numbers in ascending order: (i) 4/-9 , -5/12 ,…
  9. Arrange the following rational numbers in descending order: (i) -2 , -13/6 ,…
  10. Which of the following statements are true and which are false? (i) Every whole…
Exercise 1b
  1. (i) 1/3 (ii) 2/7 (iii) 1 3/4 (iv) 2 2/5 (v) 3 1/2 (vi) 5 5/7 (vii) 4 2/3 (viii)…
  2. (i) -1/3 (ii) -3/4 (iii) -1 2/3 (iv) -3 1/7 (v) -4 3/5 (vi) -2 5/6 (vii) -3…
  3. Which of the following statements are true and which are false? (i) -3/5 lies to…
Exercise 1c
  1. (i) -2/5 and 4/5 (ii) -6/11 and -4/11 (iii) -11/8 and 5/8 (iv) -7/3 and 1/3 (v)…
  2. (i) 3/4 and -3/5 (ii) 5/8 and -7/12 (iii) -8/9 and 11/6 (iv) -5/16 and 7/24 (v)…
  3. (i) -12/5 + 2/7 = 2/7 + -12/5 (ii) -5/8 + -9/13 = -9/13 + -5/8 (iii) 3 + -7/12 =…
  4. (i) (3/4 + -2/5) + -7/10 = 3/4 + (-2/5 + -7/10) (ii) (-7/11 + 2/-5) + -13/22 =…
  5. Fill in the blanks: (i) (-3/17) + (-12/5) = (-12/5) + (l) (ii) -9 + -21/8 = () +…
  6. Find the additive inverse of each of the following: (i) 1/3 (ii) 23/9 (iii) -18…
  7. Subtract: (i) 3/4 from 1/3 (ii) -5/6 from 1/3 (iii) -8/9 from -3/5 (iv) -9/7…
  8. Using the rearrangement property find the sum: (i) 4/3 + 3/5 + -2/3 + -11/5 (ii)…
  9. The sum of two rational numbers is -2 . If one the numbers is -14/5 find the…
  10. The sum of two rational numbers is -1/2 If one of the numbers is 5/6 find the…
  11. What number should be added to -5/8 so as to get -3/2 ?
  12. What number should be added to -1 so as to get 5/7 ?
  13. What number should be subtracted from -2/3 to get -1/6 ?
  14. (i) Which rational number is its own additive inverse? (ii) Is the difference…
Exercise 1d
  1. Find each of the following products: (i) 3/5 x -7/8 (ii) -9/2 x 5/4 (iii) -6/11…
  2. (i) 3/5 x -5/9 = -5/9 x 3/7 (ii) -8/7 x 13/9 = 13/9 x -8/7 (iii) -12/5 x 7/-36 =…
  3. (i) (5/7 x 12/13) x 7/18 = 5/7 x (12/13 x 7/18) (ii) � -13/24 x (-12/5 x 35/36)…
  4. (i) -23/17 x 18/35 = 18/35 x (l) (ii) -38 x -7/19 = -7/19 x (l) (iii) (15/7 x…
  5. Find the multiplicative inverse (i.e., reciprocal) of: (i) 13/25 (ii) -17/12…
  6. Find the value of: (i) (5/8)^-1 (ii) (-4/9)^-1 (iii) (-7)^-1 (iv) (1/-3)^-1…
  7. Verify the following: (i) 3/7 x (5/6 + 12/13) = (3/7 x 5/6) + (3/7 x 12/13) (ii)…
  8. Name the property of multiplication illustrated by each of the following…
  9. (i) The product of a rational number and its reciprocal is........ (ii) Zero…
Exercise 1e
  1. Simplify: (i) 4/9 / -5/12 (ii) -8 / -7/16 (iii) -12/7 / (-18) (iv) -1/10 / -8/5…
  2. (i) 13/5 / 26/10 = 26/10 / 13/5 (ii) -9 / 3/4 = 3/4 / (-9) (iii) -8/9 / -4/3 =…
  3. (i) (5/9 / 1/3) / 5/2 = 5/9 / (1/3 / 5/2) (ii) (-16) / 6/5 / -9/10 = (-16) / 6/5…
  4. The product of two rational numbers is -9. If one of the numbers is -12, find…
  5. The product of two rational numbers is -16/9 .If one of the numbers is -4/3 find…
  6. By what rational number should we multiply -15/56 to get -5/7 ?
  7. By what rational number should -8/39 be multiplied to obtain 1/26 ?…
  8. By what number should -33/8 be divided to get -11/2 ?
  9. Divide the sum of 13/5 and -12/7 by the product of -31/7 and 1/-2…
  10. Divide the sum of 65/12 and 8/3 by their differ-renice.
  11. Fill in the blanks: (i) 9/8 / (l) = -3/2 (ii) (l) / (-7/5) = 10/19 (iii) (l) /…
  12. (i) Are rational numbers always closed under division? (ii) Are rational…
Exercise 1f
  1. Find a rational number between 1/4 and 1/3
  2. Find a rational number between 2 and 3 .
  3. Find a rational number between -1/3 and 1/2
  4. Find two rational numbers between -3 and -2 .
  5. Find three rational numbers between 4 and 5
  6. Find three rational numbers between 2/3 and 3/4
  7. Find 10 rational numbers between -3/4 and 5/6
  8. Find 12 rational numbers between -1and 2.
Exercise 1g
  1. From a rope 11 m long. two pieces of lengths 2 3/5 m and 3 3/10 m are cut off.…
  2. A drum full of rice weight 40 1/6 kg. If the empty drum weight 13 3/4 kg. Find…
  3. A basket contains three types of fruits weight 19 1/3 kg in all. If 8 1/9 kg of…
  4. On one day a rickshaw puller earned Rs. 160. Out of his earnings he spent 26 3/5…
  5. Find the cost of 3 2/5 meters of cloth at Rs. 63 3/4 per meter.
  6. A car is moving at an average speed of 60 2/5 km/hr. How much distance will it…
  7. Find the area of a rectangular park which is 36 3/5 m long and 16 2/3 m board.…
  8. Find the area of square plot of land whose each side measure 8 1/2 meters.…
  9. One liters of petrol costs Rs. 63 3/4 What is the cost of 34 liters of petrol?…
  10. An aeroplane covers 1020 km in an hour. How much distance will it cover in 4…
  11. The cost of 3 1/2 meters of cloth is Rs. 166 1/4 . What is the cost of one…
  12. A cord of length 71 1/2 m has been cut into 26 pieces of equal length. What is…
  13. The area of a room is 65 1/4 m^2 . If its breadth is 5 7/16 meters, what is its…
  14. The product of two fractions is 9 3/5 If one of the fractions is 9 3/7 find the…
  15. In a school , 5/8 of the students are boys. If there are 240 girls, find the…
  16. After reading 7/9 of a book, 40 pages are left. How many pages are there in the…
  17. Rita had Rs. 300. She spent 1/3 of her money on notebooks and 1/4 of the…
  18. Amit earns Rs. 32000 per month. He spends 1/4 of his income on food; 3/10 of…
  19. If 3/5 of a number exceeds its 2/7 by 44 , find the number.
  20. At a cricket test match 2/7 of the spectators were in a covered place while…
Exercise 1h
  1. (-5/16 + 7/12) = ? Options A. - 7/48 B. 1/24 C. 13/48 D. 1/3
  2. (8/-15 + 4/-3) = ? Options A. 28/15 B. -28/15 C. -4/5 D. -4/15
  3. (7/-26 + 16/39) = ? Options A. 11/78 B. -11/78 C. 11/39 D. -11/39…
  4. (3 + 5/-7) = ? Options A. -16/7 B. 16/7 C. -26/7 D. -8/7
  5. (31/-4 + -5/8) = ? Options A. 67/8 B. 57/8 C. -57/8 D. -67/8
  6. What should be added to 7/12 to get -4/15 ? Options A. 17/20 B. -17/20 C. 7/20…
  7. (2/3 + -4/5 + 7/15 + -11/20) = ? Options A. -1/5 B. -4/15 C. -13/60 D. -7/30…
  8. The sum of two numbers is -4/7 to get 5/6 ? Options A. 5/2 B. 3/2 C. 5/4 D. -5/2…
  9. What should be added to -5/7 to get -2/3 ? Options A. -29/21 B. 29/21 C. 1/21 D.…
  10. What should be subtracted from -5/3 to get 5/6 ? Options A. 5/2 B. 3/2 C. 5/4…
  11. (-3/7)^-1 = ? Options A. 7/3 B. -7/3 C. 3/7 D. none of these
  12. The product of two rational numbers is -28/81 . If one of the numbers is 14/27…
  13. The product of two numbers is -16/35 . If one of the numbers is -15/14 the…
  14. What should be subtracted from -3/5 to get -2? Options A. -7/5 B. -13/5 C. 13/5…
  15. The sum of two rational numbers is -3 If one of them is -10/3 then the other…
  16. Which of the following numbers is in standard form? Options A. -12/26 B. -49/71…
  17. (-9/16 x 8/15) = ? Options A. -3/10 B. -4/15 C. -9/25 D. -2/5
  18. (-5/9 / 2/3) = ? Options A. -5/2 B. -5/6 C. -10/27 D. -6/5
  19. 4/9 / ? = -18/15 Options A. -32/45 B. -8/5 C. -9/10 D. -5/6
  20. Additive inverse of -5/9 is Options A. -9/5 B. 0 C. 5/9 D. 9/5
  21. Reciprocal of -3/4 is Options A. 4/3 B. 3/4 C. -4/3 D. 0
  22. A rational number between -2/3 and 1/4 is Options A. 5/2 B. -5/12 C. 5/24 D.…
  23. The reciprocal of a negative rational number Options A. is a positive rational…
Cce Test Paper-1
  1. Find the additive inverse of(i) 7/-10 (ii) 8/5
  2. The sum of two rational numbers is -4 If one of them is -11/5 find the other.…
  3. What number should be added to -3/5 to get 2/3 ?
  4. What number should be subtracted from to get -1/2 ?
  5. Find the multiplicative inverse of (i) -3/4 (ii) 11/4
  6. The product of two numbers is -8 . If one of them is -12 , find the other.…
  7. Evaluate: (i) -3/5 x 10/7 (ii) (-5/8)^-1 (iii) (-6)^-1
  8. Name the property of multiplication shown by each of the following statements: (i)…
  9. Find two rational numbers lying between -1/3 and 1/2
  10. What should be added to -3/5 to get ? Options A. 4/5 B. 8/15 C. 4/15 D. 2/5…
  11. What should be added to -2/3 to get 3/4 ? Options A. -11/12 B. -13/12 C. -5/4 D. 1.7…
  12. (-5/4)^-1 = ? Options A. 4/5 B. -4/5 C. 5/4 D. 3/5
  13. The product of two numbers is -1/4 If one of them is -3/10 then the other is Options…
  14. (-5/6 / -2/3) = ? Options A. -5/4 B. 5/4 C. -4/5 D. 4/5
  15. 4/3 / ? = -5/2 Options A. -8/5 B. 8/5 C. -8/15 D. 8/15
  16. Reciprocal of -7/9 is Options A. 9/7 B. -9/7 C. 7/9 D. none of these…
  17. A rational number between -2/3 and 1/2 is Options A. -1/6 B. -1/12 C. -5/6 D. 5/6…
  18. Fill in the blanks. (i) 25/8 / (l .) = - 10 (ii) -8/9 x (l l) = -2/3 (iii) (-1) + (l…
  19. Write ‘T’ for true and ‘F’ for false for each of the following: (i) Rational numbers…

Exercise 1a
Question 1.

Expressas a rational number with denominator

(i) 20 (ii) -30 (iii) 35 (iv) -40


Answer:

For a fraction,



Where, n ≠ 0


(i) We have to express as a rational number with denominator 20.


In order to make the denominator 20, multiply 5 by 4.


Therefore,




(ii) We have to express as a rational number with denominator -30.


In order to make the denominator -30, multiply 5 by -6.


Therefore,




(iii) We have to express as a rational number with denominator 35.


In order to make the denominator 35, multiply 5 by 7.


Therefore,




(iv) We have to express as a rational number with denominator -40.


In order to make the denominator 20, multiply 5 by -8.


Therefore,





Question 2.

Expressas a rational number with denominator 7.


Answer:

For a fraction,



Where, n ≠ 0 and n divides both a and b


(i) We have to express as a rational number with denominator 7.


In order to make the denominator 7, divide 98 by 14.


Therefore,





Question 3.

Expressas a rational number with denominator 5.


Answer:

For a fraction,



Where, n ≠ 0 and n divides both a and b


We have to express as a rational number with denominator 5.


In order to make the denominator 5, divide 60 by 12.


Therefore,





Question 4.

Express each of the following rational numbers in standard form:

(i) (ii) (iii) (iv)


Answer:

A rational number is in standard or simplest or lowest form when-


1. Numerator and denominator have only 1 as its highest common factor.


2. Denominator is a positive integer.


(i) The HCF of 12 and 30 is 6


Therefore,




(ii) The HCF of 49 and 14 is 7


Therefore,




(iii) The HCF of 24 and 64 is 8


Therefore,




In order, to make the denominator positive, multiply both numerator and denominator by -1




(iv) The HCF of 36 and 63 is 9


Therefore,




In order, to make the denominator positive, multiply both numerator and denominator by -1





Question 5.

Which of the two rational numbers is greater in the given pair?

(i) or 0 (ii)or 0 (iii)or

(iv)or (v)or (vi)or


Answer:

(i) is a positive number and all positive numbers are greater than 0.


Therefore,


(ii) is a negative number and all negative numbers are less than 0.


Therefore,


(iii) Both and have the same denominator 4.


Therefore, we can directly compare both the numbers.


Since, 1 > -3


Therefore,


(iv) Both and have the same denominator 7.


Therefore, we can directly compare both the numbers.


Since, -4 > -5


Therefore,


(v) and have different denominators.


Therefore, we take LCM of 3 and 4 that is 12.


Now,



And,



Since, 9 > 8


Therefore,


Hence,


(vi) We can write


and have different denominators.


Therefore, we take LCM of 1 and 2 that is 2.


Now,



And,



Since, -1 > -2


Therefore,


Hence,



Question 6.

Which of the two rational numbers is greater in the given pair?

(i)or (ii)or (iii)or

(iv)or(v)or (vi)or


Answer:

(i) and have different denominators.


Therefore, we take LCM of 3 and 7 that is 21.


Now,



And,



Since, -24 > -28


Therefore,


Hence,


(ii)



and have different denominators.


Therefore, we take LCM of 9 and 8 that is 72.


Now,



And,



Since, -45 > -56


Therefore,


Hence,


(iii)



and have different denominators.


Therefore, we take LCM of 3 and 5 that is 15.


Now,



And,



Since, -5 > -12


Therefore,


Hence,


(iv)



And,



and have different denominators.


Therefore, we take LCM of 13 and 12 that is 156.


Now,



And,



Since, -91 > -108


Therefore,


Hence,


(v)



and have different denominators.


Therefore, we take LCM of 10 and 5 that is 10.


Now,



And,



Since, -7 > -8


Therefore,


Hence,


(vi)


We can write


and have different denominators.


Therefore, we take LCM of 1 and 5 that is 5.


Now,



And,



Since, -12 > -15


Therefore,


Hence,



Question 7.

Fill in the blanks with the correct symbol out of >, = and <:

(i) (ii)(iii)

(iv) (v) (vi)


Answer:

(i) Clearly,



(ii)



and have different denominators.


Therefore, we take LCM of 13 and 91 that is 91.


Now,



And,



Clearly,


Hence,



(iii) We can write


and have different denominators.


Therefore, we take LCM of 1 and 5 that is 5.


Now,



And,



Since, -10 > -13


Therefore,


Hence,


(iv)


and have different denominators.


Therefore, we take LCM of 3 and 8 that is 24.


Now,



And,



Since, -16 < -15


Therefore,


Hence,


(v)



is a positive number and all positive numbers are greater than 0.


Therefore,


Hence,


(vi) and have different denominators.


Therefore, we take LCM of 9 and 10 that is 90.


Now,



And,



Since, -80 > -81


Therefore,


Hence,



Question 8.

Arrange the following rational numbers in ascending order:

(i) (ii)

(iii) (iv)


Answer:

(i)



And,



Since, the denominators of all the numbers are different therefore we will take LCM of the denominators.


LCM of 9, 12, 18 and 3 = 36






Clearly,


-24 < -16 < -15 < -14


Therefore,



Hence,



(ii)



And,



Since, the denominators of all the numbers are different therefore we will take LCM of the denominators.


LCM of 4, 12, 16 and 24 = 48






Clearly,


-36 < -21 < -20 < -18


Therefore,



Hence,



(iii)



Since, the denominators of all the numbers are different therefore we will take LCM of the denominators.


LCM of 5, 10, 15 and 20 = 60






Clearly,


-44 < -42 < -39 < -36


Therefore,



Hence,



(iv)



Since, the denominators of all the numbers are different therefore we will take LCM of the denominators.


LCM of 7, 14, 28 and 42 = 84






Clearly,


-54 < -48 < -46 < -39


Therefore,



Hence,




Question 9.

Arrange the following rational numbers in descending order:

(i) (ii)

(iii) (iv)


Answer:

(i)



And,



Since, the denominators of all the numbers are different therefore we will take LCM of the denominators.


LCM of 1, 6and 3 = 6






Clearly,


2 > -12 > -13 > -16


Therefore,



Hence,



(ii)



And,



Since, the denominators of all the numbers are different therefore we will take LCM of the denominators.


LCM of 10, 15, 20 and 30 = 60






Clearly,


-18>-28>-33>-34


Therefore,



Hence,



(iii)



Since, the denominators of all the numbers are different therefore we will take LCM of the denominators.


LCM of 6, 12, 18 and 24 = 72






Clearly,


-42>-52>-60>-69


Therefore,



Hence,



(iv)


Since, the denominators of all the numbers are different therefore we will take LCM of the denominators.


LCM of 11, 22, 33 and 44 = 132






Clearly,


-92>-114>-117>-120


Therefore,



Hence,




Question 10.

Which of the following statements are true and which are false?

(i) Every whole number is a rational number.

(ii) Every integer is a rational number.

(iii) 0 is a whole number but it is not a rational number.


Answer:

(i) Every whole number a can be represented as


Therefore, every whole number is a rational number.


(ii) Every integer a can be represented as


Therefore, every integer is a rational number.


(iii) 0 can be represented as


Therefore, 0 is a whole number and a rational number.




Exercise 1b
Question 1.

Represent each of the following numbers on the number line:

(i) (ii) (iii)(iv)

(v) (vi) (vii)(viii)


Answer:

(i) is greater than 0 and less than 1.


Therefore, it lies between 0 and 1



(ii) is greater than 0 and less than 1.


Therefore, it lies between 0 and 1



(iii)


is greater than 1 and less than 2.


Therefore, it lies between 1 and 2



(iv)


is greater than 2 and less than 3.


Therefore, it lies between 2 and 3.



(v)


is greater than 3 and less than 4.


Therefore, it lies between 3 and 4.



(vi)


is greater than 5 and less than 6.


Therefore, it lies between 5 and 6.



(vii)


is greater than 4 and less than 5.


Therefore, it lies between 4 and 5.



(viii) The number line representation of 8 is




Question 2.

Represent each of the following numbers on the number line:

(i) (ii) (iii) (iv)

(v) (vi) (vii) (viii)


Answer:

(i) is greater than -1 and less than 0.


Therefore, it lies between -1 and 0



(ii) is greater than -1 and less than 0.


Therefore, it lies between -1 and 0



(iii)


is greater than -2 and less than -1`.


Therefore, it lies between -2 and -1



(iv)


is greater than -8 and less than -7`.


Therefore, it lies between -8 and -7



(v)


is greater than -5 and less than -4.


Therefore, it lies between -5 and -4



(vi)


is greater than -3 and less than -2.


Therefore, it lies between -3 and -2



(vii) The number line representation of -3 is



(viii)


is greater than -3 and less than -2.


Therefore, it lies between -3 and -2




Question 3.

Which of the following statements are true and which are false?

(i) lies to the left of 0 on the number line.

(ii)lies to the right of 0 on the number line.

(iii) The rational numbersandare on opposite sides of 0 on the number line.

(iv) The rational numberlies to the left of 0 on the number line.


Answer:

(i) True


is a negative number.


All negative numbers are less than 0 and therefore, lie to the left of 0 on the number line.


Hence, lies to the left of 0 on the number line.


(iii) False


is a negative number.


All negative numbers are less than 0 and therefore, lie to the left of 0 on the number line.


Hence, lies to the left of 0 on the number line.


(iii)True


is a positive number.


All positive numbers are greater than 0 and therefore, lie to the right of 0 on the number line.


Hence, lies to the right of 0 on the number line.


is a negative number.


All negative numbers are less than 0 and therefore, lie to the left of 0 on the number line.


Hence, lies to the left of 0 on the number line.


Therefore, the rational numbers, and are on opposite sides of 0 on the number line.


(iv) False



is a positive number.


All positive numbers are greater than 0 and therefore, lie to the right of 0 on the number line.


Hence, lies to the right of 0 on the number line.




Exercise 1c
Question 1.

Add the following rational numbers:

(i)and (ii)and (iii)and

(iv)and (v)and (vi)and


Answer:

(i)




(ii)





(iii)




To convert it into lowest terms, divide both numerator and denominator by common divisor of both 6 and 8 that is, 2




(iv)




To convert it into lowest terms, divide both numerator and denominator by common divisor of both 6 and 3 that is, 3.




=2


(v)





To convert it into lowest terms, divide both numerator and denominator by common divisor of both 4 and 6 that is, 2.




(vi)




To convert it into lowest terms, divide both numerator and denominator by common divisor of both 18 and 15 that is, 3.





Question 2.

Add the following rational numbers:

(i) and (ii) and (iii)and

(iv)and (v)and

(vi)and (vii)and

(viii)and (ix)and


Answer:

(i) Since, the denominators of given rational numbers are different therefore, we take their LCM.


LCM of 4 and 5 = 20



And



Now,







(ii) Since, the denominators of given rational numbers are different therefore, we take their LCM.


LCM of 8 and 12 = 24



And



Now,







(iii) Since, the denominators of given rational numbers are different therefore, we take their LCM.


LCM of 9 and 6 = 18



And



Now,






(iv) Since, the denominators of given rational numbers are different therefore, we take their LCM.


LCM of 16 and 24 = 48



And



Now,






(v) Since, the denominators of given rational numbers are negative therefore, we will make them positive.



Now, since, the denominators of given rational numbers are different therefore, we take their LCM.


LCM of 18 and 27 = 54



And



Now,






(vi) Since, the denominators of given rational numbers are negative therefore, we will make them positive.



And,



Now, since, the denominators of given rational numbers are different therefore, we take their LCM.


LCM of 12 and 15 = 60



And



Now,






(vii) We can write -1 as .


Now, since, the denominators of given rational numbers are different therefore, we take their LCM.


LCM of 1 and 4 = 4



And



Now,





(viii) We can write 2 as .


Now, since, the denominators of given rational numbers are different therefore, we take their LCM.


LCM of 1 and 4 = 4



And



Now,






(ix)


On adding, any number to 0 we get the same number.


Therefore,




Question 3.

Verify the following:

(i) (ii)

(iii)(iv)


Answer:

(i)LCM of 5 and 7 = 35



And,




Similarly,


LCM of 7 and 5 = 35



And,




i.e., LHS = RHS


Hence,



Verified


(ii)LCM of 13 and 8 = 104



And,




Similarly,


LCM of 8 and 13 = 104



And,




i.e., LHS = RHS


Hence,



Verified


(iii) 3 can be written as


LCM of 1 and 12 = 12



And,




Similarly,


LCM of 1 and 12 = 12



And,




i.e., LHS = RHS


Hence,



Verified


(iv) Since, the denominators are negative we will make them positive.



And,



LCM of 7 and 35 = 35



And,




Similarly,


LCM of 7 and 5 = 35



And,




i.e., LHS = RHS


Hence,



Verified



Question 4.

Verify the following:

(i)

(ii)

(iii)


Answer:

(i)


















RHS = LHS


Verified


(ii)



















RHS = LHS


Verified


(iii)



















RHS = LHS


Verified



Question 5.

Fill in the blanks:

(i)

(ii)

(iii)

(iv)

(v)

(vi)


Answer:

(i)


By Commutative property, i.e., a+b=b+a


Therefore,



(ii)


By Commutative property, i.e., a+b=b+a


Therefore,



(iii)


By Associative property, i.e., (a+b)+c=a+(b+c)


Therefore,



(iv)


By Associative property, i.e., (a+b)+c=a+(b+c)


Therefore,



(v)


By Associative property, i.e., (a+b)+c=a+(b+c)


Therefore,



(vi) 0,0


0 is the additive identity that is, if we add 0 to any number the result will be the number itself.


a+0=0+a


Also, By Commutative property, i.e., a+b=b+a


We get,




Question 6.

Find the additive inverse of each of the following:

(i) (ii) (iii) (iv) (v)

(vi) (vii) (viii) (ix) (x)


Answer:

Additive inverse of a number is the number such that,


Therefore,


(i) Additive inverse of is


(ii) Additive inverse of is


(iii) Additive inverse of -18 is 18


(iv) Additive inverse of is


(v)



Therefore, Additive inverse of is


(vi)



Additive inverse of is


(vii) Additive inverse of is


(viii) Additive inverse of is


(ix)



Therefore, Additive inverse of is


(x)



Additive inverse of is



Question 7.

Subtract:

(i)from (ii)from

(iii)from (iv)from

(v)from (vi)from

(vii)from (viii)from


Answer:

(i)


Since the denominators of both the numbers are different therefore, we will take their LCM


LCM 0f 3 and 4 = 12



And,



Therefore,






(ii)


Since the denominators of both the numbers are different therefore, we will take their LCM


LCM 0f 6 and 3 = 6



And,



Therefore,







(iii)


Since the denominators of both the numbers are different therefore, we will take their LCM


LCM 0f 9 and 5 = 45



And,



Therefore,







(iv)


We can write,


Since the denominators of both the numbers are different therefore, we will take their LCM


LCM 0f 1 and 7 =7



And,



Therefore,







(v)


We can write,


Since the denominators of both the numbers are different therefore, we will take their LCM


LCM 0f 1 and 11 = 11



And,



Therefore,







(vi)





(vii)


Since the denominators of both the numbers are different therefore, we will take their LCM


LCM 0f 13 and 5 = 65



And,



Therefore,







(viii)


We can write,


Since the denominators of both the numbers are different therefore, we will take their LCM


LCM 0f 1 and 7 = 7



And,



Therefore,








Question 8.

Using the rearrangement property find the sum:

(i)

(ii)

(iii)

(iv)


Answer:

Rearrangement property says that, the numbers in an addition expression may be arranged and grouped in any order.


Therefore,


(i)


We arrange the numbers with same denominators together,





Now, we take LCM of 3 and 5=15



And,



Therefore,







(ii)



We arrange the numbers,



LCM of 3 and 6 =6



And,



LCM of 4 and 8 =8



And,



Now,





Now, we take LCM of 6 and 8=24



And,



Therefore,






In lowest terms,



(iii)



We arrange the numbers,



LCM of 20 and 10 =20



And,



LCM of 14 and 7 =14



And,



Now,





Now, we take LCM of 20 and 14=140



And,



Therefore,






(iv)



We arrange the numbers,



LCM of 4 and 9 =18



And,



Now,






In lowest terms,



Now, we take LCM of 1 and 18=18



And,



Therefore,








Question 9.

The sum of two rational numbers is. If one the numbers isfind the other.


Answer:

Sum of two rational numbers = -2


One number =


Let the other rational number = x


Now,


According to question,







Therefore, the other rational number is



Question 10.

The sum of two rational numbers isIf one of the numbers isfind the other.


Answer:

Sum of two rational numbers =


One number =


Let the other rational number = x


Now,


According to question,






In lowest terms,



Therefore, the other rational number is



Question 11.

What number should be added toso as to get?


Answer:

Let the number = x


Now,


According to question,







Therefore, should be added to so as to get



Question 12.

What number should be added toso as to get?


Answer:

Let the number = x


Now,


According to question,







Therefore, should be added to so as to get



Question 13.

What number should be subtracted fromto get?


Answer:

Let the number = x


Now,


According to question,







In lowest terms,



Therefore, should be subtracted from so as to get



Question 14.

(i) Which rational number is its own additive inverse?

(ii) Is the difference of two rational numbers a rational number?

(iii) Is addition commutative on rational numbers?

(iv) Is addition associative on rational numbers?

(v) Is subtraction commutative on rational numbers?

(vi) Is subtraction associative on rational numbers?

(vii) What is the negative of a negative rational number?


Answer:

(i) A Additive inverse of a number is the number such that,


0 is the rational number that is its own additive inverse


(ii) Let there be 2 rational numbers, and where, b≠0 and d≠0



LCM of b and d = bd



Where, bd ≠ 0


Therefore, is a rational number


Hence,


Yes, the difference of two rational numbers a rational number


(iii) Yes, addition is commutative on rational numbers


Let there be 2 rational numbers, and where, b≠0 and d≠0


Then,



(iv) Yes, addition is associative on rational numbers


Let there be 3 rational numbers, , and where, b≠0 , d≠0 and f≠0


Then,



(v) No, subtraction is not commutative on rational numbers


Let there be 2 rational numbers, and where, b≠0 and d≠0


Then,



(vi) No, addition is not associative on rational numbers


Let there be 3 rational numbers, , and where, b≠0 , d≠0 and f≠0


Then,



(vii) Negative of a negative rational number is the number itself without the negative sign.




Exercise 1d
Question 1.

Find each of the following products:

(i) (ii) (iii)

(iv) (v) (vi)

(vii) (viii) (ix)

(x) (xi)

(xii)


Answer:

(i)





(ii)





(iii)





In lowest terms,



(iv)





In lowest terms,



(v)





In lowest terms,



Further,



(vi)





In lowest terms,



(vii)





In lowest terms,



(viii)





In lowest terms,



Further,



(ix)





In lowest terms,



(x)






In lowest terms,



Further,



(xi)






In lowest terms,



Further,



(xii)






In lowest terms,




Question 2.

Verify each of the following:

(i) (ii)

(iii)

(iv)


Answer:

(i)





In lowest terms,






In lowest terms,



LHS=RHS


Verified


(ii)








LHS=RHS


Verified


(iii)





In lowest terms,






In lowest terms,



LHS=RHS


Verified


(iv)





In lowest terms,






In lowest terms,



LHS=RHS


Verified



Question 3.

Verify each of the following:

(i)

(ii) �

(iii)


Answer:

(i)








In lowest terms,







In lowest terms,



LHS=RHS


Verified


(ii)








In lowest terms,



Further,








In lowest terms,



Further,



LHS=RHS


Verified


(iii)








In lowest terms,



Further,








In lowest terms,



Further,



LHS=RHS


Verified



Question 4.

Fill in the blanks:

(i)

(ii)

(iii)

(iv)


Answer:

(i)


By Commutative Property, i.e, a × b = b × a



(ii)


By Commutative Property, i.e, a × b = b × a



(iii)


By Associative Property, i.e, (a × b) × c = a × (b × c)



(iv)


By Associative Property, i.e, (a × b) × c = a × (b × c)




Question 5.

Find the multiplicative inverse (i.e., reciprocal) of:

(i) (ii) (iii) (iv) (v)

(vi) (vii) (viii) (ix) (x)


Answer:

A multiplicative inverse for a number x, is a number which when multiplied by x yields the multiplicative identity, 1


The multiplicative inverse of a rational number is.


Therefore,


(i) The multiplicative inverse of =.


(ii) The multiplicative inverse of =.


In standard form,



(iii) The multiplicative inverse of =.


In standard form,



.


(iv) The multiplicative inverse of =.


(v) The multiplicative inverse of =.



(vi) The multiplicative inverse of =.


In standard form,



(vii) The multiplicative inverse of -1 =-1.


(viii) The multiplicative inverse of is undefined.


Since, is undefined.


(ix) The multiplicative inverse of =.


(x) The multiplicative inverse of =.


In standard form,




Question 6.

Find the value of:

(i)(ii) (iii) (iv)


Answer:

Let there be a rational number then =


Therefore,


(i)



(ii)



(iii)



(iv)




Question 7.

Verify the following:

(i)

(ii)

(iii)

(iv)


Answer:

(i)









In lowest terms,









In lowest terms,



LHS=RHS


Verified


(ii)









In lowest terms,









In lowest terms,



LHS=RHS


Verified


(iii)









In lowest terms,









In lowest terms,



LHS=RHS


Verified


(iv)









In lowest terms,









In lowest terms,



LHS=RHS


Verified



Question 8.

Name the property of multiplication illustrated by each of the following statements:

(i)

(ii)

(iii)

(iv)

(v)

(vi)


Answer:

(i) Commutative law i.e., a b = b a


(ii) Associative law i.e., a(bc) = (ab)c


(iii) Distributive law i.e., a(b + c) = ab + ac


(iv) Property of multiplicative identity i.e., a× 1=1× a


(v) Property of multiplicative inverse i.e., =1


(vi) Multiplicative property of 0 i.e., a× 0=0



Question 9.

Fill in the blanks:

(i) The product of a rational number and its reciprocal is........

(ii) Zero has……reciprocal.

(iii) The numbers…… and….are their own reciprocals.

(iv) Zero is……the reciprocal of any number.

(v) The reciprocal ofwhereis……

(vi) The reciprocal ofwhereis……

(vii) The reciprocal of a positive rational number is……

(viii) The reciprocal of a negative rational number is……


Answer:

(i) 1


(ii) No


(iii) 1 and -1


(iv) Not


(v)


(vi) a


(vii) Positive


(viii) Negative




Exercise 1e
Question 1.

Simplify:

(i)(ii) (iii)(iv) (v) (vi)


Answer:

(i)






In lowest terms,



(ii)







(iii)







In lowest terms,



(iv)






In lowest terms,



(v)






In lowest terms,



(vi)






In lowest terms,



Further,




Question 2.

Verify whether the given statement is true or false:

(i)

(ii)

(iii)

(iv)


Answer:

(i)











Since, RHS = LHS


Therefore, True


(ii)











Since, RHS ≠ LHS


Therefore, False


(iii)











Since, RHS ≠ LHS


Therefore, False


(iv)











Since, RHS ≠ LHS


Therefore, False



Question 3.

Verify whether the given statement is true or false:

(i)

(ii)

(iii)


Answer:

(i)
















RHS ≠ LHS


Hence, False


(ii)


















RHS ≠ LHS


Hence, False


(iii)


















RHS ≠ LHS


Hence, False



Question 4.

The product of two rational numbers is -9. If one of the numbers is -12, find the other.


Answer:

Product of two rational numbers = -9


One rational number = -12


Let the other rational number = x


Now,


According to the question,


-12 × x = -9





Hence, the other rational number is



Question 5.

The product of two rational numbers is .If one of the numbers is find the other.


Answer:

Product of two rational numbers =


One rational number =


Let the other rational number = x


Now,


According to the question,








Hence, the other rational number is



Question 6.

By what rational number should we multiply to get ?


Answer:

Let x be multiplied by to get


It can be written as,








Hence, it should be multiplied by is



Question 7.

By what rational number should be multiplied to obtain ?


Answer:

Let x be multiplied by to get


It can be written as,








Hence, it should be multiplied by is



Question 8.

By what number should be divided to get ?


Answer:

Let be divided by x to get


It can be written as,








Hence, it should be multiplied by is



Question 9.

Divide the sum of and by the product of and


Answer:

Sum of and -






Product of and -






Now,


According to the question,






Question 10.

Divide the sum of and by their differ-renice.


Answer:

According to the question,









Question 11.

Fill in the blanks:

(i) (ii)

(iii) (iv)


Answer:

(i)








Therefore,



(ii)






Therefore,



(iii)






Therefore,



(iv)








Therefore,




Question 12.

(i) Are rational numbers always closed under division?

(ii) Are rational numbers always commutative under division?

(iii) Are rational numbers always associative under division?

(iv) Can we divide 1 by 0?


Answer:

(i) No rational numbers are not always closed under division,


Since, which is not a rational number


(ii) No rational numbers are not always commutative under division,


Let and be two rational numbers.



And



Therefore,



Hence, rational numbers are not always commutative under division


(iii) No rational numbers are not always associative under division,


Let , and be two rational numbers.



And



Therefore,



Hence, rational numbers are not always associative under division.


(iv) No we cannot divide 1 by 0.


Since, which is not defined.




Exercise 1f
Question 1.

Find a rational number betweenand


Answer:

To find a rational number x between two rational numbers and , we use



Therefore, to find rational number x (let) between and








Question 2.

Find a rational number betweenand.


Answer:

To find a rational number x between two rational numbers and , we use



Therefore, to find rational number x (let) between 2 and 3






Question 3.

Find a rational number betweenand


Answer:

To find a rational number x between two rational numbers and , we use



Therefore, to find rational number x (let) between and








Question 4.

Find two rational numbers betweenand.


Answer:

To find a rational number x between two rational numbers and , we use



Therefore, to find rational number x (let) between -3 and -2






Now if we find a rational number between and -2 it will also be between -3 and -2 since lies between -3 and -2


Therefore, to find rational number y (let) between and -2







Question 5.

Find three rational numbers betweenand


Answer:

To find a rational number x between two rational numbers and , we use



Therefore, to find rational number x (let) between 4 and 5





Now if we find a rational number between and it will also be between 4 and 5 since lies between 4 and 5


Therefore, to find rational number y (let) between and






Now if we find a rational number between and 5it will also be between 4 and 5 since lies between 4 and 5


Therefore, to find rational number z (let) between and 5







Question 6.

Find three rational numbers betweenand


Answer:

To find a rational number x between two rational numbers and , we use



Therefore, to find rational number x (let) between and






Now if we find a rational number between and it will also be between and since lies between and


Therefore, to find rational number y (let) between and






Now if we find a rational number between andit will also be between and since lies between and


Therefore, to find rational number z (let) betweenand







Question 7.

Find 10 rational numbers betweenand


Answer:

We can write as (Since,


And,


We can write as (Since,


Now clearly, rational numbers between them are,



Any 10 rational numbers are,




Question 8.

Find 12 rational numbers between -1and 2.


Answer:

We can write as (Since,


And,


We can write 2 as (Since,


Now clearly any 12 rational numbers between -1 and 2 are,





Exercise 1g
Question 1.

From a rope 11 m long. two pieces of lengthsm andm are cut off. What is the length of remaining rope?


Answer:

Length of rope = 11 m


Length of first piece cut = 2


Length of second piece cut = 3


Total length cut = Length of first piece cut + Length of second piece cut







Length of remaining rope = Length of rope - Total length cut






Hence, Length of remaining rope =



Question 2.

A drum full of rice weight kg. If the empty drum weight kg. Find the weight of rice in the drum.


Answer:

Weight of drum full of rice = kg


Weight of empty drum = kg


Weight of rice Weight of drum full of rice - Weight of empty drum







Hence, Weight of rice =



Question 3.

A basket contains three types of fruits weightkg in all. Ifkg of these be apples,kg be oranges and the rest pears, what is the weight of the pears in the basket?


Answer:

Weight of basket with three types of fruits = kg


Weight of apples = kg


Weight of oranges = kg


Weight of pears = Weight of basket with three types of fruits – (Weight of apples + Weight of oranges )









Hence, Weight of pears



Question 4.

On one day a rickshaw puller earned Rs. 160. Out of his earnings he spenton tea and snacks, Rs.on food and Rs.on repairs of the rickshaw. How much did he save on that day?


Answer:

Total Earnings = Rs 160


Spend on tea and snacks = Rs


Spend on food = Rs


Spend on repairs = Rs


Total Expenditure = Spend on tea and snacks + Spend on food + Spend on repairs






Savings= Total Earnings - Total Expenditure






Hence, Savings =



Question 5.

Find the cost ofmeters of cloth at Rs.per meter.


Answer:

Cost of cloth per meter =


Total meters =


Cost of total cloth = Cost of cloth per meter × Total meters






Therefore, total cost



Question 6.

A car is moving at an average speed ofkm/hr. How much distance will it cover inhours?


Answer:

Speed of car =


Total hours =


Total Distance = Speed of car × Total hours







Therefore, Total Distance



Question 7.

Find the area of a rectangular park which ism long andm board.


Answer:

Length of park =


Breadth of park =


Area of park = Length of park × Breadth of park







Hence, Area of park



Question 8.

Find the area of square plot of land whose each side measuremeters.


Answer:

Side of plot =


Area of plot = Side of plot × Side of plot







Hence, Area of plot



Question 9.

One liters of petrol costs Rs.What is the cost of 34 liters of petrol?


Answer:

Cost of one litre petrol =


Cost of 34 litre petrol = 34 × Cost of one litre petrol







Cost of 34 litre petrol



Question 10.

An aeroplane covers 1020 km in an hour. How much distance will it cover inhours?


Answer:

Distance covered in one hour = 1020 km


Distance covered in hours = × Distance covered in one hour







Distance covered in hours



Question 11.

The cost ofmeters of cloth is Rs.. What is the cost of one metre of cloth?


Answer:

Cost of of cloth = Rs


Cost of of cloth = Cost of of cloth







Cost of of cloth



Question 12.

A cord of lengthm has been cut into 26 pieces of equal length. What is the length of each piece?


Answer:

Length of cord = 71


No of pieces = 26


Length of each piece = Length of cord No of pieces










Length of each piece



Question 13.

The area of a room is. If its breadth ismeters, what is its length?


Answer:

Area of room =


Breadth of room =


Length of room = Area of room Breadth of room







Length of room



Question 14.

The product of two fractions isIf one of the fractions isfind the other.


Answer:

Product of two fractions = 9


First fraction = 9


Second fraction = Product of two fractions ÷ First fraction








Second fraction



Question 15.

In a schoolof the students are boys. If there are 240 girls, find the number of boys in the school.


Answer:

Fraction of boys =


Fraction of girls =1- =


Number of girls= 240


Number of girls = Total students ×


⇒ 240 = Total students ×


⇒ Total students = 240 ÷





Total students =640


Number of boys = Total students - Number of girls


=640 – 240 = 400


Number of boys= 400



Question 16.

After readingof a book, 40 pages are left. How many pages are there in the book?


Answer:

Fraction read =


Fraction left =


Pages left = 40


Pages left = Total pages


40= Total pages


⇒ Total pages =




Total pages = 180



Question 17.

Rita had Rs. 300. She spentof her money on notebooks andof the remainder on stationary items. How much money is left with her?


Answer:

Total money = Rs 300


Fraction spent on notebooks =


Amount spent on notebooks = = Rs 100


Amount left = Rs 300 – Rs 100 =Rs 200


Fraction spent on stationary =


Amount spent on stationary = = Rs 50


Money left = Rs 300 – Rs 150 = Rs 150



Question 18.

Amit earns Rs. 32000 per month. He spendsof his income on food;of the remainder on house rent andof the remainder on the education of children. How much money is still left with him?


Answer:

Total earnings = Rs 32000


Amount spend on food =


Amount left = Rs 32000 - Rs 8000 = Rs 24000


Amount spend on house rent =


Amount left = Rs 24000- Rs 7200 = Rs 16800


Amount spend on education =


Amount left = Rs 16800 - = Rs 12800


Money left = Rs 12800



Question 19.

Ifof a number exceeds itsby, find the number.


Answer:

Let the number be x


of x =


of x =


According to the question,










The number is 140



Question 20.

At a cricket test matchof the spectators were in a covered place while 15000 were in open. Find the total number of spectators.


Answer:

Fraction of spectators covered =


Fraction left =


Number of spectators in open = 15000


According to the question,


Number of spectators in open = Total number of spectators ×








Exercise 1h
Question 1.



Options A.

B.

C.

D.


Answer:


LCM of 12 and 16 = 48





Question 2.



Options A.

B.

C.

D.


Answer:


And,







Question 3.



Options A.

B.

C.

D.


Answer:






Question 4.



Options A.

B.

C.

D.


Answer:







Question 5.



Options A.

B.

C.

D.


Answer:






Question 6.

What should be added toto get

Options A.

B.

C.

D.


Answer:

Let the number added be x.


Then,







Question 7.



Options A.

B.

C.

D.


Answer:


LCM of 3, 5, 15, 20






Question 8.

The sum of two numbers isto get

Options A.

B.

C.

D.


Answer:

Let the number added be x.


Then,







Question 9.

What should be added toto get

Options A.

B.

C.

D.


Answer:

Let the number added be x.


Then,







Question 10.

What should be subtracted fromto get

Options A.

B.

C.

D.


Answer:

Let the number subtracted be x.


Then,







Question 11.



Options A.

B.

C.

D. none of these


Answer:

We know,
For any real number a≠0,

So,


Question 12.

The product of two rational numbers is. If one of the numbers isthen the other one is

Options A.

B.

C.

D.


Answer:

Let the other number be x.


Then,






Question 13.

The product of two numbers is. If one of the numbers isthe other is

Options A.

B.

C.

D.


Answer:

Let the other number be x.


Then,







Question 14.

What should be subtracted fromto get

Options A.

B.

C.

D.


Answer:

Let the number subtracted be x.


Then,







Question 15.

The sum of two rational numbers isIf one of them isthen the other one is

Options A.

B.

C.

D.


Answer:

Let the other number be x.


Then,







Question 16.

Which of the following numbers is in standard form?

Options A.

B.

C.

D.


Answer:

is not in standard form since 12 and 26 have a common divisor 2.


is not in standard form since its denominator is negative.


Therefore, only and are in standard forms as their numerator and denominator have no common divisor and their denominators are positive.


Question 17.



Options A.

B.

C.

D.


Answer:




Question 18.



Options A.

B.

C.

D.


Answer:





Question 19.



Options A.

B.

C.

D.


Answer:







Question 20.

Additive inverse ofis

Options A.

B.

C.

D.


Answer:

Additive inverse of a number is the number such that,


Therefore,


Additive inverse of is


Question 21.

Reciprocal ofis

Options A.

B.

C.

D. 0


Answer:

Reciprocal of



Question 22.

A rational number betweenandis

Options A.

B.

C.

D.


Answer:

Rational number between and







Question 23.

The reciprocal of a negative rational number

Options A. is a positive rational number

B. is a negative rational number

C. can be either a positive or a negative rational number

D. does not exist


Answer:

Let be a negative rational number


Then, its reciprocal will be which is also a negative rational number.


Hence, the reciprocal of a negative rational number is a negative rational number



Cce Test Paper-1
Question 1.

Find the additive inverse of(i)(ii)


Answer:

Additive inverse of a number is the number such that,


Therefore,


(i)


Additive inverse of is


(ii) Additive inverse of is



Question 2.

The sum of two rational numbers isIf one of them isfind the other.


Answer:

Sum of two rational numbers = -4


First number =


Second number = Sum of two rational numbers - First number






Second number



Question 3.

What number should be added toto get


Answer:

Let the number added be x


Then,








Question 4.

What number should be subtracted fromto get


Answer:

Let the number subtracted be x


Then,








Question 5.

Find the multiplicative inverse of (i)(ii)


Answer:

Multiplicative inverse of a rational number


Therefore,


(i) Negative inverse of



(ii) Negative inverse of



Question 6.

The product of two numbers is. If one of them is, find the other.


Answer:

Let the other number be x


Then,







Question 7.

Evaluate:

(i) (ii) (iii)


Answer:

(i)





(ii)




(iii)





Question 8.

Name the property of multiplication shown by each of the following statements:

(i) (ii)

(iii)

(iv)

(v)


Answer:

(i) Commutative law of multiplication i.e., a b = b a


(ii) 1 as multiplicative identity i.e., a × 1 = b × 1


(iii) Associative law of multiplication i.e., a(bc) = (ab)c


(iv) Multiplicative property of 0 i.e., a× 0=0


(v) Distributive law of multiplication over addition i.e., a(b + c) = ab + ac



Question 9.

Find two rational numbers lying betweenand


Answer:

Rational number between and







Now,


Rational number between and








Question 10.

What should be added toto get ?

Options A.

B.

C.

D.


Answer:

Let the number added be x


Then,







Question 11.

What should be added toto get

Options A.

B.

C.

D.


Answer:

Let the number added be x


Then,







Question 12.



Options A.

B.

C.

D.


Answer:



Question 13.

The product of two numbers isIf one of them isthen the other is

Options A.

B.

C.

D.


Answer:

Let the other number be x


Then,








Question 14.



Options A.

B.

C.

D.


Answer:






Question 15.



Options A.

B.

C.

D.


Answer:






Question 16.

Reciprocal ofis

Options A.

B.

C.

D. none of these


Answer:

Reciprocal of



Question 17.

A rational number betweenandis

Options A.

B.

C.

D.


Answer:

Rational number between and







Question 18.

Fill in the blanks.

(i)

(ii)

(iii)

(iv)


Answer:

(i)








(ii)








(iii)







(iv)








Question 19.

Write ‘T’ for true and ‘F’ for false for each of the following:

(i) Rational numbers are always closed under subtraction.

(ii) Rational numbers are always closed under division.

(iii)

(iv) Subtraction is commutative on rational numbers.

(v)


Answer:

(i) true


Let there be two rational numbers and


Then,



which is also a rational number


Hence, Rational numbers are always closed under subtraction.


(ii) false



Hence, Rational numbers are not always closed under division.


(iii) false



Hence,


(iv) false


Let there be two rational numbers and


Then,



And



Therefore,



Hence, Subtraction is not commutative on rational numbers.


(v) true