### Exponents and Powers - Solutions 2

CBSE Class –VIII Mathematics
NCERT Solutions
CHAPTER - 12
Exponents and Powers (Ex. 12.2)

1. Express the following numbers in standard form:
(i) 0.0000000000085
(ii) 0.00000000000942
(iii) 6020000000000000
(iv) 0.00000000837
(v) 31860000000
Ans. (i) 0.0000000000085
= 0.0000000000085   =
(ii) 0.00000000000942
= 0.00000000000942   =
(iii) 6020000000000000
= 6020000000000000   =
(iv) 0.00000000837
= 0.00000000837   =
(v) 31860000000
= 31860000000   =

2. Express the following numbers in usual form:
(i)
(ii)
(iii)
(iv)
(v)
(vi)
Ans. (i) 
(ii) 4.5  10000 = 45000
(iii)  = 0.00000003
(iv)  = 1000100000
(v)  = 5.8 x 1000000000000
= 5800000000000
(vi)  = 3.61492  1000000
= 3614920

3. Express the number appearing in the following statements in standard form:
(i)1 micron is equal to  m.
(ii) Charge of an electron is 0.000,000,000,000,000,000,16 coulomb.
(iii) Size of a bacteria is 0.0000005 m.
(iv) Size of a plant cell is
0.00001275 m.
(v) Thickness if a thick paper is 0.07 mm.
Ans. (i) 1 micron
m
(ii)Charge of an electron is
0.00000000000000000016 coulombs.
=$0.00000000000000000016×\frac{{10}^{19}}{{10}^{19}}$
coulomb
(iii) Size of bacteria = 0.0000005
$\frac{5}{10000000}=\frac{5}{1{0}^{7}}=5×1{0}^{-7}$ m
(iv) Size of a plant cell is 0.00001275 m
= 0.00001275   =  m
(v) Thickness of a thick paper = 0.07 mm
mm =  mm

4. In a stack there are 5 books each of thickness 20 mm and 5 paper sheets each of thickness 0.016 mm. What is the total thickness of the stack?
Ans. Thickness of one book = 20 mm
Thickness of 5 books = 20  5 = 100 mm
Thickness of one paper = 0.016 mm
Thickness of 5 papers = 0.016  5
= 0.08 mm
Total thickness of a stack = 100 + 0.08
=100.08 mm
= 100.08
mm