Gujarat Board 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?

- 0.0000000000085
- 0.00000000000942
- 6020000000000000
- 0.00000000837
- 31860000000

Solution:

1. 0.0000000000085 = \(\frac{85}{10000000000000}\)

= \(\frac{85}{10^{13}}\) = \(\frac{8.5 \times 10}{10^{13}}\) = 8.5 × 10 × 10^{-13}

= 8.5 × 10^{-12}

2. 0.00000000000942

= \(\frac{942}{100000000000000}=\frac{942}{10^{14}}=\frac{9.42 \times 10^{2}}{10^{14}}\)

= 9.42 × 10^{2} × 10^{-14} = 9.42 × 10^{-12}

3. 6020000000000000

= 602 × 10000000000000 = 602 × 10^{13}

= 6.02 × 10^{2} × 10^{13} = 6.02 × 10^{15}

4. 0.00000000837 = \(\frac{837}{100000000000}=\frac{837}{10^{11}}\)

= \(\frac{8.37 \times 10^{2}}{10^{11}}\) = 8.37 × 10^{2} × 10^{-11}

= 8.37 × 10^{2+(-11)} = 8.37 × 10^{-9}

5. 3186000000 = 3186 × 1000000

= 3186 × 10^{7} = 3.186 × 10^{3} × 10^{7}

= 3186 × 10^{3+7} = 3.186 × 10^{10}

Question 2.

Express the following numbers in usual form?

Solution:

- 3.02 × 10
^{-6} - 4.5 × 10
^{4} - 3 × 10
^{-8} - 1.0001 × 10
^{9} - 5.8 × 10
^{12} - 3.61492 × 10
^{6}

Solution:

1. 3.02 × 10^{-6} = 302 × 10^{-2} × 10^{-6}

= 302 × 10^{-8}

= 361492 × 10 = 3614920

Question 3.

Express the number appearing in the following statements in standard form?

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

Solution:

∴ Thickness of a thick paper is 7 × 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:

∵ Thickness of one book = 20 mm

∴ Thickness of 5 books = 5 × 20 mm = 100 mm

Again,

Thickness of I paper sheet = 0.016 mm

∴ Thickness of 5 paper sheets

= 5 × 0,016 mm

= 0.080 m

∴ Total thickness = 100 mm + 0.080 mm

= 100.08 mm

= 1.0008 × 10^{2} mm.