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Important questions for Exponents Class 8 Chapter 12 CBSE



In this page we have Important questions for exponents Class 8 maths Chapter 12 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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