Buy BOOKS at Discounted Price

Exponents

Class 8th Mathematics Part Ii Karnataka Board Solution
Exercise 10.1
  1. 1728 Express the following numbers in the exponential form:
  2. 1/512 Express the following numbers in the exponential form:
  3. 0.000169. Express the following numbers in the exponential form:
  4. 12345 Write the following numbers using base 10 and exponents:
  5. 1010.0101 Write the following numbers using base 10 and exponents:…
  6. 0.1020304 Write the following numbers using base 10 and exponents:…
  7. Find the value of (−0.2)-4
Exercise 10.2
  1. 3^1 × 3^2 × 3^3 × 3^4 × 3^5 × 3^6 . Simplify:
  2. 2^2 × 3^3 × 2^4 × 3^5 × 3^6 . Simplify:
  3. How many zeros are there in 10^4 × 10^3 × 10^2 × 10?
  4. Which is larger: (5^3 × 5^4 × 5^5 × 5^6) or (5^7 × 5^8)?
Exercise 10.3
  1. 10−1 × 10^2 × 10−3 × 10^4 × 10−5 × 10^6 ; Simplify:
  2. 2^3 x 3^2 x 5^4/3^3 x 5^2 x 2^4 . Simplify:
  3. Which is larger: (3^4 × 2^3) or (2^5 × 3^2)?
  4. Suppose m and n are distinct integers. Can 3^m x 2^n/2^m x 3^n be an integer?…
  5. Suppose b is a positive integer such that 2^4/b^2 is also an integer. What are…
Exercise 10.4
  1. (2^5)^6 x (3^3)^2/(2^6)^5 x (3^2)^3 Simplify:
  2. (5^-3)^2 x 3^4/(3^-2)^-3 x (5^3)^-2 Simplify:
  3. Can you find two integers m,n such that 2m + n = 2mn ?
  4. If (2m)^4 = 4^6 , find the value of m.
Exercise 10.5
  1. 6^8 x 5^3/10^3 x 3^4 Simplify:
  2. (15)^-3 x (-12)^4/5^-6 x (36)^2 Simplify:
  3. (0.22)^4 x (0.222)^3/(0.2)^5 x (0.2222)^2 Simplify:
  4. Is (10^4)^3/5^13 an integer? Justify your answer.
  5. Which is larger : (100)^4 or (125)^3 ?
Exercise 10.6
  1. (2/3)^8 x (6/4)^3 Simplify:
  2. (1.8)^6 × (4.2)-3 Simplify:
  3. (0.0006)^9/(0.015)^-4 Simplify:
  4. Can it happen that for some integer m ≠ 0, (4/25)^m = (2/5)^m^2 ?…
  5. Find all positive integers m,n such that (3m)n = 3m × 3n.
Exercise 10.7
  1. (12)^6/162 Use the laws of exponents and simplify.
  2. 3^-4 x 10^-5 x (625)/5^-3 x 6^-4 Use the laws of exponents and simplify.…
  3. 2^3^2/(2^3)^2 Use the laws of exponents and simplify.
  4. What is the value of (10^3)^2 x 10^-4/10^2 ?
  5. Simplify: (b^-3 b^7 (b^-1)^2/(-b)^2 (b^2)^3)^-2
  6. (3^2)^2 − ((−2)^3)^2 − (− (5^2))^2 ; Find the value of each of the following…
  7. ((0.6)^2)^0 − ((4.5)^0)−2 ; Find the value of each of the following…
  8. (4^-1)^4 x 2^5 x (1/16)^3 x (8^-2)^5 x (64^2)^3 Find the value of each of the…
Additional Problems 10
  1. The value of (3m)n, for every pair of integers (m,n), isA. 3m+n B. 3mn C. 3mn D. 3m +…
  2. If x,y, 2x + y/2 are nonzero real numbers, then (2x + y/2)^-1 (2x)^-1 + (y/2)^-1…
  3. If 2x − 2x−2 = 192, the value of x isA. 5 B. 6 C. 7 D. 8
  4. The number (6^(6^6))^1/6 is equal toA. 6^6 B. 6^6^6 - 1 C. 6^(6^5) D. 6^(5^6)…
  5. The number of pairs positive integers (m,n)such that mn =25 isA. 0 B. 1 C. 2 D. more…
  6. The diameter of the Sun is 1.4 × 10^9 meters and that of the Earth is about 1.2768 ×…
  7. (-0.75)^3 + (0.3)^-3 - (- 3/2)^-3 Find the value of each of the following expressions:…
  8. (8 x (4^2)^4 x 3^3 x 27^2) + (9 x 6^3 x 4^7 x (3^2)^3)/(24 x (6^2)^4 x (2^4)^2) + (144…
  9. (2^19 x 27^3) + (15 x 4^9 x 9^4)/(6^9 x 2^10) + 12^10 Find the value of each of the…
  10. How many digits are there in the number 2^3 × 5^4 × 20^5 ?
  11. If a^7 = 3, find the value of (a^-2)^-3 x (a^3)^4 x (a^-17)^-1/a^7 .…
  12. If 2m × a^2 = 2^8 , where a,m are positive integers, find all possible values of a + m.…
  13. Suppose 3k × b^2 = 6^4 for some positive integers k, b. Find all possible values of k +…
  14. Find the value of (625)^6.25 x (25)^2.60/(625)^7.25 x (5)^1.20 .
  15. A person had some rupees which is a power of 5. He gave a part of it to his friend…

Exercise 10.1
Question 1.

Express the following numbers in the exponential form:

1728


Answer:

We prime factorize the number

1728 = 33× 26


⇒ 1728 = 33× 43


Since the powers are same so the bases can be multiplied


⇒ 1728 = 123



Question 2.

Express the following numbers in the exponential form:



Answer:

We prime factorize the number 512

512 = 29


Since reciprocal of a number results in negative power,


So = 2-9



Question 3.

Express the following numbers in the exponential form:

0.000169.


Answer:

We prime factorize the number 169

169 = 132


So we can say that


0.000169 = 132× 10-6


⇒ 0.000169 = (13× 10-3)2


⇒ 0.000169 = 0.0132



Question 4.

Write the following numbers using base 10 and exponents:

12345


Answer:

The number can be expanded by expressing the number in terms of its digits and multiplying each digit with 10 raised to a specific power according to its place value

12345 = 1×104 + 2×103 + 3×102 + 4×10 + 5



Question 5.

Write the following numbers using base 10 and exponents:

1010.0101


Answer:




Question 6.

Write the following numbers using base 10 and exponents:

0.1020304


Answer:




Question 7.

Find the value of (−0.2)-4


Answer:

Since the power is negative so





Exercise 10.2
Question 1.

Simplify:

31 × 32 × 33 × 34 × 35 × 36 .


Answer:

Since the bases are same so the powers can be added

31 × 32 × 33 × 34 × 35 × 36 = 3(1 + 2 + 3 + 4 + 5 + 6)


⇒ 31 × 32 × 33 × 34 × 35 × 36 = 321



Question 2.

Simplify:

22 × 33 × 24 × 35 × 36.


Answer:

Since there are two bases so their powers can be separately added.

22 × 33 × 24 × 35 × 36 = 2(2 + 4) × 3(3 + 5 + 6)


⇒ 22 × 33 × 24 × 35 × 36 = 26 × 314



Question 3.

How many zeros are there in 104 × 103 × 102 × 10?


Answer:

Since the bases are same so the powers can be added

104 × 103 × 102 × 10 = 10(4 + 3 + 2 + 1)


⇒ 104 × 103 × 102 × 10 = 1010


Since the power of 10 is 10 so there are 10 zeroes.



Question 4.

Which is larger: (53 × 54 × 55 × 56) or (57 × 58)?


Answer:

53 × 54 × 55 × 56 = 5(3 + 4 + 5 + 6)

⇒ 53 × 54 × 55 × 56 = 518


57 × 58 = 5(7 + 8)


⇒ 57 × 58 = 515


Since the power of 5 in 53 × 54 × 55 × 56 is greater so 53 × 54 × 55 × 56 is greater than 57 × 58




Exercise 10.3
Question 1.

Simplify:

10−1 × 102 × 10−3 × 104 × 10−5 × 106;


Answer:

Since the bases are same so their powers are solved algebraically

10−1 × 102 × 10−3 × 104 × 10−5 × 106 = 10(-1 + 2-3 + 4-5 + 6)


On solving we get,


⇒ 10−1 × 102 × 10−3 × 104 × 10−5 × 106 = 103



Question 2.

Simplify:

.


Answer:


Since the denominator and numerator have common base so their powers can be subtracted





Question 3.

Which is larger: (34 × 23) or (25 × 32)?


Answer:

We divide the two expressions


Since the denominator and numerator have common base so their powers can be subtracted



Since the fraction is greater than 1 so (34 × 23) is greater than (25 × 32)



Question 4.

Suppose m and n are distinct integers. Can be an integer? Give reasons.


Answer:

We divide the two expressions


Since the denominator and numerator have common base so their powers can be subtracted



Since m and n are two distinct integers so the power can never become 0 and hence the fraction can never an integer.



Question 5.

Suppose b is a positive integer such that is also an integer. What are the possible values of b?


Answer:

Since is an integer so

the numerator must be greater than denominator



So b has to be either 1,2 or 4 to become an integer.




Exercise 10.4
Question 1.

Simplify:



Answer:




Question 2.

Simplify:



Answer:




Question 3.

Can you find two integers m,n such that 2m + n = 2mn ?


Answer:

2m + n = 2mn

⇒ m + n = mn


Let m = n


So we get


2m = m2


⇒ m = 2


Since m = n, so


n = 2



Question 4.

If (2m)4 = 46, find the value of m.


Answer:

(2m)4 = 46

⇒ (4m)2 = 46


Since the bases are same so their powers can be equated


2m = 6


⇒ m = 3




Exercise 10.5
Question 1.

Simplify:



Answer:



Since the bases are common in numerator and denominator so their powers are subtracted




Question 2.

Simplify:



Answer:




Since the bases are common in numerator and denominator so their powers are subtracted




Question 3.

Simplify:



Answer:







Question 4.

Is an integer? Justify your answer.


Answer:




Since after reducing the expression there is a 5 in the denominator but no multiple of 5 in the numerator so it is not an integer



Question 5.

Which is larger : (100)4 or (125)3?


Answer:

We divide the two numbers




Since the numerator is greater than the denominator so 1004 is greater than 1253




Exercise 10.6
Question 1.

Simplify:



Answer:




Since bases are same so the powers can be subtracted




Question 2.

Simplify:

(1.8)6 × (4.2)-3


Answer:

(1.8)6 × (4.2)-3 = (18×10-1)6×(42×10-1)-3

⇒ (1.8)6 × (4.2)-3 = (32×2×10-1)6×(7×3×2×10-1)-3


⇒ (1.8)6 × (4.2)-3 = 312×26×10-6×7-3×3-3×2-3×103


⇒ (1.8)6 × (4.2)-3 = 39×23×7-3×10-3





Question 3.

Simplify:



Answer:







Question 4.

Can it happen that for some integer m ≠ 0, ?


Answer:



Since the bases are same so the powers can be equated


2m = m2


⇒ m = 2


So it can happen when m = 2



Question 5.

Find all positive integers m,n such that (3m)n = 3m × 3n.


Answer:

(3m)n = 3m × 3n

⇒ 3mn = 3m + n


Since the bases are same so the powers can be equated


mn = m + n


Let m = n


⇒ m2 = 2m


⇒ m = 2


Answer: m = 2, n = 2




Exercise 10.7
Question 1.

Use the laws of exponents and simplify.



Answer:

126 = (4×3)6

⇒ 126 = 212×36


On prime factorizing 162 we get


162 = 2× 34





Question 2.

Use the laws of exponents and simplify.



Answer:





Question 3.

Use the laws of exponents and simplify.



Answer:




Question 4.

What is the value of


Answer:




Question 5.

Simplify:



Answer:





Question 6.

Find the value of each of the following expressions:

(32)2 − ((−2)3)2 − ( − (52))2 ;


Answer:

(32)2 = 92 = 81

((−2)3)2 = (-8)2 = 64


( − (52))2 = (-25)2 = 625


So the value of the expression is


(32)2 − ((−2)3)2 − ( − (52))2 = 81-64-625 = -608



Question 7.

Find the value of each of the following expressions:

((0.6)2)0 − ((4.5)0)−2 ;


Answer:

The value of any number raised to the power zero is always 1

((0.6)2)0 = 1


(4.5)0 = 1


⇒ 1-2 = 1


So the solution of the expression is


((0.6)2)0 − ((4.5)0)−2 = 1-1 = 0



Question 8.

Find the value of each of the following expressions:








Answer:

(4-1)4 = 4-4

⇒ (4-1)4 = 2-8




(8-2)5 = (2-6)5


⇒ (8-2)5 = 2-30


(642)3 = (212)3


(642)3 = 236


= 2-8×25×2-12×2-30×236


= 2-9




Additional Problems 10
Question 1.

The value of (3m)n, for every pair of integers (m,n), is
A. 3m+n

B. 3mn

C. 3mn

D. 3m + 3n


Answer:

Using the third law of exponents, If a ≠0 is a number and m, n are integers, then(am)n= amn


So, (3m)n = 3mn


Question 2.

If x,y, are nonzero real numbers, then

equals
A. 1

B. x ⋅ y

C. x ⋅ y

D. 1/xy


Answer:


For a number a ≠ 0, we define



It is given that x,y, are nonzero real numbers,





Question 3.

If 2x − 2x−2 = 192, the value of x is
A. 5

B. 6

C. 7

D. 8


Answer:

Given 2x − 2x−2 = 192


⇒2x–2x.2−2 = 192


Taking 2x common from both the terms,


⇒2x (1 - 2−2) = 192


For a number a ≠ 0and natural number n, we define







⇒2x = 64× 4


⇒2x = 26 × 22


For any a ≠ 0, and integers m,n, am × an = am+n


⇒2x = 28


Hence, x = 8


Question 4.

The number is equal to
A. 66

B.

C.

D.


Answer:


Using the third law of exponents, If a ≠0 is a number and m, n are integers, then (am)n= amn



For a number a ≠ 0, we define




For any a ≠ 0, and integers m,n, am × an = am+n



Question 5.

The number of pairs positive integers (m,n)such that mn =25 is
A. 0

B. 1

C. 2

D. more than 2


Answer:

Given mn =25


⇒mn = 52


⇒ (m, n) = (5, 2)


Hence, only 1 such pair of positive integers is possible.


Question 6.

The diameter of the Sun is 1.4 × 109 meters and that of the Earth is about 1.2768 × 107 meters. Find the approximate ratio of the diameter of the Sun to that of the Earth.


Answer:

Given the diameter of the Sun = 1.4 × 109 meter


And the diameter of the Earth is = 1.2768 × 107 meters


Ratio of the diameter of the sun and that of the earth =


For any number a ≠ 0 and positive integers m and n, not necessarily distinct,



Ratio of the diameter of the sun and that of the earth =


Ratio of the diameter of the sun and that of the earth =



Question 7.

Find the value of each of the following expressions:



Answer:



{Using For a number a ≠ 0, we define


}









Question 8.

Find the value of each of the following expressions:



Answer:

Using the third law of exponents, If a ≠0 is a number and m, n are integers, then (am)n= amn




Using For a ≠0 and b ≠ 0, and integer m,


(a × b)m = am × bm






Using For any a ≠ 0, and integers m,n,


am × an = am+n












Question 9.

Find the value of each of the following expressions:



Answer:


Using For a ≠0 and b ≠ 0, and integer m,


(a × b)m = am × bm



Using For any a ≠ 0, and integers m, n,


am × an = am+n







Question 10.

How many digits are there in the number 23 × 54 × 205?


Answer:

23 × 54 × 205 = 23 × 54 × (4× 5)5


Using For a ≠0 and b ≠ 0, and integer m,


(a × b)m = am × bm


⇒23 × 54 × 205 = 23 × 54 × 45× 55


⇒23 × 54 × 205 = 23 × 54 × (22 )5× 55


Using third law of exponents, If a ≠0 is a number and m, n are integers, then (am)n= amn


⇒23 × 54 × 205 = 23 × 54 × 210× 55


Using For any a ≠ 0, and integers m, n,


am × an = am+n


⇒23 × 54 × 205 = 23+10 × 54+5


⇒23 × 54 × 205 = 213 × 59


We know that 2× 5 = 10


So, 23 × 54 × 205 = (29 × 59)× 24


⇒23 × 54 × 205 = 109 × 16


⇒23 × 54 × 205 =16000000000


Hence, there are 11 digits in the given number.



Question 11.

If a7 = 3, find the value of .


Answer:

Given: a7 = 3



{Using the third law of exponents, If a ≠0 is a number and m, n are integers, then (am)n= amn}



{UsingFor any a ≠ 0, and integers m, n,


am × an = am+n}



For any number a ≠ 0 and positive integers m and n, not necessarily distinct,








Question 12.

If 2m × a2 = 28, where a,m are positive integers, find all possible values of a + m.


Answer:

Given: 2m × a2 = 28


⇒2m × a2 = 28× 12


Then a + m = 8 + 1 = 9


Also, 2m × a2 = 24 × 42


Then a + m = 4 +4 = 8


Similarly, 2m × a2 = 22× 82


Then a + m = 2 +8 = 10



Question 13.

Suppose 3k × b2 = 64 for some positive integers k, b. Find all possible values of k + b.


Answer:

Given: 3k × b2 = 64


⇒3k × b2 = (2× 3)4


Using For a ≠0 and b ≠ 0, and integer m,


(a × b)m = am × bm


⇒3k × b2 = 24× 34


⇒3k × b2 = 42× 34


On comparing,


k = 4, b = 4


⇒ k+b = 8



Question 14.

Find the value of .


Answer:


Using the third law of exponents, If a ≠0 is a number and m, n are integers, then (am)n= amn



Using For any a ≠ 0, and integers m, n,


am × an = am+n






Question 15.

A person had some rupees which is a power of 5. He gave a part of it to his friend which is also a power of 5. He was left with ₹ 500. How much did money he have?


Answer:

Let the money he have be Rs 5x and that he gave to his friend be Rs 5y, such that x>y.


According to the question,


5x - 5y = 500


We can see from the equation that 5x> 500 because 500 is the money that he is left with.


So 5x = 625


⇒ x = 4


Then 625 - 5y = 500


⇒5y = 125


⇒ y = 3


So, the money he had = Rs 625 and that he gave to his friend = Rs 125