In this page we have ** Important questions for exponents Class 8 CBSE**
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**Question 1 **

Evaluate

- 2
^{ -2} - (- 2)
^{ - 2} - (3/2)
^{-5 }

**Answer**

As we know that

b^{-n}= 1/b^{n}

(i) 2^{-2} = 1/ 2^{2} =1/4

(ii) (-2)^{-2} = 1/(-2)^{2}= 1/4

(iii) (3/2)^{-5 } =3-^{5}/ 2^{-5}

=2^{5}/3^{5 }= 32/243

**Question 2 **

Simplify and express the result in power notation with positive exponent.

(i) (-2)^{5} ÷ (-2)^{4}

(ii) (1/2)^{2} × (2/5)^{2}

(iii) (-5)^{2} × (3/5)

**Answer **

(i) (-2)^{5} ÷ (-2)^{4}

= (-2)^{5} / (-2)^{4}

= (-2)^{5-4}

=-2

(ii) (1/2)^{2} × (2/5)^{2}

= (1/4) X (4/25)

= 1/25

iii) (-5)^{2} × (3/5)

=25 × (3/5)

=15

**Question 3**

Find the value of.

- (4
^{0}+ 4^{ - 1}) × 2^{2} - (3
^{ - 1}× 9^{ - 1}) ÷ 3^{ - 2} - (11
^{ - 1}+ 12^{ - 1}+ 13^{ - 1})^{0}

**Answer**

- (4
^{0}+ 4^{ - 1}) × 2^{2}= (1+1/4) × 4

= 4+1=5

- (3
^{ - 1}× 9^{ - 1}) ÷ 3^{ - 2}= [(1/3) × (1/9)] ÷ (1/9)

=1/3

3. (11^{ - 1} + 12^{ - 1} + 13^{ - 1})^{0}

=1 as a^{0 }=1

** Question 4**

Find the value of x here

(11/9)^{3} x (9/11)^{6} = (11/9)^{2x-1}

**Answer**

(11/9)^{3} x (11/9)^{-6} = (11/9)^{2x-1}

(11/9)^{3-6} = (11/9)^{2x-1}

-3=2x-1

Or

x=-1

**Question 5**

Find the value of *m* for which 2* ^{m}* ÷ 2

**Answer **

2* ^{m}* ÷ 2

2^{m} × (1/2^{-4}) = 2^{10}

2^{m+4} =2^{10}

So m+4=10

m=6

**Question 6 **

Express the following numbers in standard form.

(i) 0.0000000015 (ii) 0.00000001425

(iii) 102000000000000000

**Answer **

- 0.0000000015
=1.5 ×10

^{-9} - 0.00000001425

=1.425×10^{-8}

3. 102000000000000000

=1.02×10^{17}

**Question 7**

Express the following numbers in usual form.

(i) 34.02 x 10^{-5} (ii) 9.5 x 10^{5}

(iii) 9 x 10^{-4} (iv) 2.0001 x 10^{8}

**Answer**

- 34.02 x 10
^{-5}= .0003402

2. 9.5 x 10^{5}

=950000

3. 9 x 10^{-4}

=.0009

4. 2.0001 x 10^{8}

=200010000

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