NCERT Solutions Class 8 Maths Chapter 12 Exponents and Powers Ex 12.2

NCERT Solutions Class 8 Mathematics 
Chapter – 12 (Exponents and Powers) 

The NCERT Solutions in English Language for Class 8 Mathematics Chapter – 12 Exponents and Powers Exercise 12.2 has been provided here to help the students in solving the questions from this exercise. 

Chapter 12: Exponents and Powers

• NCERT Solution Class 8 Maths Ex – 12.1

Exercise – 12.2 

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

Solution –

(i) 0.0000000000085
= 0.0000000000085 ×
= 8.5 ×10^-12

(ii) 0.00000000000942
= 0.00000000000942 ×
= 9.42×10^-12

(iii) 6020000000000000
= 6020000000000000 ×
= 6.02×10¹⁵

(iv) 0.00000000837
= 0.00000000837 ×
= 8.37×10^-9

(v) 31860000000
= 31860000000 ×
= 3.186×10¹⁰

2. Express the following numbers in the usual form.
(i) 3.02×10^-6
(ii) 4.5×10⁴
(iii) 3×10^-8
(iv) 1.0001×10⁹
(v) 5.8×10¹²
(vi) 3.61492×10⁶

Solution –

(i) 3.02×10^-6
=
= 0 .00000302

(ii) 4.5×10⁴
= 4.5×10000
= 45000

(iii) 3×10^-8
=
= 0.00000003

(iv) 1.0001×10⁹
= 1000100000

(v) 5.8×10¹²
= 5.8×1000000000000
= 5800000000000

(vi) 3.61492×10⁶
= 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 bacteria is 0.0000005 m
(iv)  Size of a plant cell is 0.00001275 m
(v) Thickness of a thick paper is 0.07 mm

Solution –
(i) 1 micron =
=
= 1×10^-6

(ii) Charge of an electron is 0.00000000000000000016 coulombs
= 0.00000000000000000016 ×
= 1.6×10^-19 coulomb

(iii) Size of bacteria = 0.0000005
= 

=
= 5×10^-7 m

(iv) Size of a plant cell is 0.00001275 m
= 0.00001275 ×
= 1.275 × 10^-5m

(v) Thickness of a thick paper = 0.07 mm
0.07 mm
= mm

=

= 7×10^-2 mm

4. In a stack, there are 5 books, each having a thickness of 20 mm and 5 paper sheets, each having a thickness of 0.016 mm. What is the total thickness of the stack?

Solution – 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
mm