# GSEB Solutions Class 8 Maths Chapter 12 Exponents and Powers Ex 12.2

Gujarat BoardĀ GSEB Textbook Solutions Class 8 Maths Chapter 12 Exponents and Powers Ex 12.2 Textbook Questions and Answers.

## Gujarat Board Textbook Solutions Class 8 Maths Chapter 12 Exponents and Powers Ex 12.2

Question 1.
Express the following numbers in standard form?

1. 0.0000000000085
2. 0.00000000000942
3. 6020000000000000
4. 0.00000000837
5. 31860000000

Solution:
1. 0.0000000000085 = $$\frac{85}{10000000000000}$$
= $$\frac{85}{10^{13}}$$ = $$\frac{8.5 \times 10}{10^{13}}$$ = 8.5 Ć 10 Ć 10-13
= 8.5 Ć 10-12

2. 0.00000000000942
= $$\frac{942}{100000000000000}=\frac{942}{10^{14}}=\frac{9.42 \times 10^{2}}{10^{14}}$$
= 9.42 Ć 102 Ć 10-14 = 9.42 Ć 10-12

3. 6020000000000000
= 602 Ć 10000000000000 = 602 Ć 1013
= 6.02 Ć 102 Ć 1013 = 6.02 Ć 1015

4. 0.00000000837 = $$\frac{837}{100000000000}=\frac{837}{10^{11}}$$
= $$\frac{8.37 \times 10^{2}}{10^{11}}$$ = 8.37 Ć 102 Ć 10-11
= 8.37 Ć 102+(-11) = 8.37 Ć 10-9

5. 3186000000 = 3186 Ć 1000000
= 3186 Ć 107 = 3.186 Ć 103 Ć 107
= 3186 Ć 103+7 = 3.186 Ć 1010

Question 2.
Express the following numbers in usual form?
Solution:

1. 3.02 Ć 10-6
2. 4.5 Ć 104
3. 3 Ć 10-8
4. 1.0001 Ć 109
5. 5.8 Ć 1012
6. 3.61492 Ć 106

Solution:
1. 3.02 Ć 10-6 = 302 Ć 10-2 Ć 10-6
= 302 Ć 10-8

= 361492 Ć 10 = 3614920

Question 3.
Express the number appearing in the following statements in standard form?

1. 1 micron is equal to $$\frac{1}{1000000}$$ m.
2. Charge of an electron is 0.000,000,000.000,000,000,16 coulomb.
3. Size of a bacteria is 0.0000005 m.
4. Size of a plant cell is 0.00001275 m.
5. Thickness of a thick paper is 0.07 mm.

Solution:

ā“ Thickness of a thick paper is 7 Ć 10-2 mm.

Question 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?
Solution:
āµ Thickness of one book = 20 mm
ā“ Thickness of 5 books = 5 Ć 20 mm = 100 mm
Again,
Thickness of I paper sheet = 0.016 mm
ā“ Thickness of 5 paper sheets
= 5 Ć 0,016 mm
= 0.080 m
ā“ Total thickness = 100 mm + 0.080 mm
= 100.08 mm
= 1.0008 Ć 102 mm.