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Published on: 27/07/2018
In this chapter Exponents and Powers contains important questions in CBSE 8th Standard Mathematics. It also covered with most important questions in Exponents and Powers.
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Questions + Answers key
Take MCQ Mathematics Test

1.
Find the value of x: 3, if x = (100)1- 4 ÷ (100)0
2.
Express the following numbers in usual form.
5.8 x 1012
3.
Find the multiplicative inverse of the following numbers.
\((\frac{1}{3^{2}})^{-1}\)
4.
Expand the following numbers using exponents.
36025.248
5.
Evaluate {\((\frac{1}{3})^{-1}-(\frac{1}{4})^{-1}\)}-1
6.
Expand the following numbers using exponents.
1256.249
7.
Find the multiplicative inverse of the following:
10-100
8.
Find the multiplicative inverse of the following:
5-3
9.
Find the multiplicative inverse of the following:
10-5
10.
By what number should (-15)1 be divided, so that quotient may be equal to (-15)-1?
11.
Solve the following:
\((\frac{1}{2})^{-2}\div(\frac{1}{2})^{-3}\)
12.
Find the usual form of the number \(\frac{3\times 10^{4}}{2\times 10^{8}}\)
13.
If a = - 1and b = 2, then find the value of the following:
(i) ab + ba
(ii) ab - ba
(iii) ab x ba
(iv) ab ÷ ba
14.
Express the product of 1.3x104 and 3.4x10-2 in the standard form.
15.
The usual form of 2.08 x 10-5 is
0.0000208
0.000028
0.000208
0.0002080
16.
The value of 52 x 5-2 is
1
5
54
5-4
17.
The reciprocal of \((\frac{3}{7})^{-1}\)is
\(\frac{7}{3}\)
\(-\frac{3}{7}\)
\(-\frac{7}{3}\)
\(\frac{3}{7}\)
18.
5-2 can be written as
\(\frac{1}{5}\)
\(\frac{1}{5^{2}}\)
52
-\(\frac{2}{5}\)
19.
In 3n, n is known as
base
constant
exponent
variable
20.
The standard form of \(\frac{1}{10000000000}\) is ____________
21.
The value of(4-1 + 2-1 + 3-1)1 is _____________
22.
The value of \((\frac{1}{2^{3}})^{2}\) is equal to __________
23.
The value of \(\frac{1}{7^{-3}}\) is equal to 216.
24.
3829.26= 3 x 1000 + 8 x 100 + 2 x 10 + 9 + 2 x 10-1 + 6 x 10-2
= 3 x 103 + 8 x 102 + 2 x 101 + 9 x 10° + 2x 10-1 +6 X 10-2
1.
∵ x=(100)1-4 ÷ (100)0=(100)-3 [∵ (100)0=1]
∴ \(x^{-3}=\frac{1}{x^{3}}=\frac { 1 }{ \left\{ { \left( 100 \right) }^{ -3 } \right\} ^{ 3 } } =\frac{1}{100^{-9}}\) [∵ (am)n=amn]
= 1009
2.
We have, 5.8 x 1012 = 5.8 x 1000000000000
= 5800000000000
3.
32
4.
36025.248= \(3\times10^{4}+6\times10^{3}+2\times10^{1}+5\times10^{0}+2\times10^{-1}+4\times10^{-2}+8\times10^{-3}\)
5.
We have , {\((\frac{1}{3})^{-1}-(\frac{1}{4})^{-1}\)}-1
\(\left\{ \frac { { \left( 1 \right) }^{ -1 } }{ { \left( 3 \right) }^{ -1 } } -\frac { { \left( 1 \right) }^{ -1 } }{ { \left( 4 \right) }^{ -1 } } \right\} ^{ -1 }\quad \quad \quad \left[ \because \quad \left( \frac { a }{ b } \right) ^{ m }=\frac { { a }^{ m } }{ { b }^{ m } } \quad \right] \)
\(=\left\{ \frac { 3 }{ 1 } -\frac { 4 }{ 1 } \right\} ^{ -1 }\quad \quad \quad \left[ \because \quad { a }^{ -m }=\frac { 1 }{ { a }^{ m } } \right] \)
= (3-4)-1 = (-1)-1=\(\frac{1}{(-1)^{1}}\) \( \left[ \because \quad { a }^{ -m }=\frac { 1 }{ { a }^{ m } } \right] \)
=\(\frac{1}{-1}=-1\)
6.
We have, 1256.249
=1\(\times\)1000+2\(\times\)100+5\(\times\)10+6\(\times\)1+\(\frac{2}{10}+\frac{4}{100}+\frac{9}{1000}\)
\(=1\times 10^{3}+2\times 10^{2}+5\times 10^{1}+6\times 10^{0}+2\times 10^{-1}+4\times 10^{-2}+9\times 10^{-3}\)
7.
Multiplicative inverse of 10-100 is 10100.
8.
Multiplicative inverse of 5-3 is 53.
9.
We have,10-5=\(\frac{1}{10^{5}}\)
Reciprocal of \(\frac{1}{10^{5}}\)=105
∴ Multiplicative inverse of 10-5 is 105. [\(10^{-5}\times 10^{5}=10^{0}=1\)]
10.
Let x be the required number.
Then, \(\frac{(-15)^{-1}}{x}=(-15)^{-1}\)
=\(\frac{1}{(-15)x}=\frac{1}{(-15)}\) [∵ \((a)^{-1}=\frac{1}{a}\)]
⇒ \(\frac{1}{x}=1 ⇒ x=1\)
So, (-15)-1 should be divided by 1 to get quotient (-15)-1.
11.
\((\frac{1}{2})^{-2}\div(\frac{1}{2})^{-3}\)=\((\frac{1}{2})^{-2}\times(\frac{1}{2})^{-3}\)
= \((\frac{1}{2})^{-2+3}=(\frac{1}{2})^{1}=\frac{1}{2}\)
12.
0.00015
13.
(i) We have, ab + ba = (-1)2 + (2)-1= 1+\(\frac{1}{2}\)
=\(\frac{2+1}{2}=\frac{3}{2}\)
(ii) We have, ab - ba=(-1)2-(2)-1 [∵ an=\(\frac{1}{a^{n}}\)]
=1-\(\frac{1}{2}\)=\(\frac{2-1}{2}=\frac{1}{2}\)
(iii) We have,ab x ba=(-1)2x(2)-1=1x\(\frac{1}{2}\)=\(\frac{1}{2}\) [∵ an=\(\frac{1}{a^{n}}\)]
(iv) We have, ab ÷ ba=(-1)÷(2)-1=\((-1)^{2}\times \frac{1}{(2)^{-1}}\)
=1x2=2 [∵ \(\frac{1}{a^{-n}}\)=an]
14.
4.42 X102
15.
(a)
0.0000208
16.
(a)
1
17.
(d)
\(\frac{3}{7}\)
18.
(b)
\(\frac{1}{5^{2}}\)
19.
(c)
exponent
20.
( )
10-10
21.
( )
\(\frac{12}{13}\)
22.
( )
\(\frac{1}{64}\)
23.
(b)
24.
(a)
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