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Important questions for Exponents Class 8 CBSE


In this page we have Important questions for exponents Class 8 CBSE . Hope you like them and do not forget to like , social share and comment at the end of the page.

Question 1  

Evaluate

  1. 2 -2
  2. (- 2) - 2
  3.  (3/2)-5   


Answer

As we know that

b-n= 1/bn

(i)  2-2  =  1/ 22  =1/4

(ii) (-2)-2  = 1/(-2)2= 1/4

(iii) (3/2)-5   =3-5/ 2-5 

=25/35   = 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.

  1. (40 + 4 - 1) × 22
  2.  (3 - 1 × 9 - 1)  ÷ 3 - 2
  3. (11 - 1 + 12 - 1 + 13 - 1)0


Answer

  1. (40 + 4 - 1) × 22

    = (1+1/4) × 4

    = 4+1=5

     

  2. (3 - 1 × 9 - 1)  ÷ 3 - 2

    = [(1/3) × (1/9)] ÷ (1/9)

         =1/3

     

         3. (11 - 1 + 12 - 1 + 13 - 1)0

            =1   as  a0 =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 2m   ÷  2-4 = 45

Answer

2m   ÷   2-4 = 45

2m × (1/2-4)  = 210

2m+4 =210

So  m+4=10

m=6

Question 6

Express the following numbers in standard form.

(i) 0.0000000015 (ii) 0.00000001425

(iii) 102000000000000000


Answer

  1. 0.0000000015

    =1.5 ×10-9

     

  2. 0.00000001425
    =1.425×10-8

     

     3. 102000000000000000

=1.02×1017

 

Question 7

Express the following numbers in usual form.

(i) 34.02 x 10-5 (ii) 9.5 x 105

(iii) 9 x 10-4 (iv) 2.0001 x 108


Answer

  1. 34.02 x 10-5

    = .0003402

 

      2. 9.5 x 105

     =950000

    3. 9 x 10-4

    =.0009

    4. 2.0001 x 108

=200010000

 

 

 

 


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