HBSE 8th Class Maths Solutions Chapter 12 Exponents and Powers Ex 12.2

Haryana State Board HBSE 8th Class Maths Solutions Chapter 12 Exponents and Powers Ex 12.2 Textbook Exercise Questions and Answers.

Haryana Board 8th Class Maths Solutions Chapter 12 Exponents and Powers Exercise 12.2

Question 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
= \(\frac{85}{10000000000000}\)
= \(\frac{8.5 \times 10}{10^{13}}\)
= 8.5 × 10¹ × 10^-13
= 8.5 × 10^-12

(ii) 0.00000000000942
= \(\frac{942}{100000000000000}\)
= \(\frac{9.42 \times 100}{10^{14}}\)
= 9.42 × 10² × 10^-14
= 9.42 × 10^-12

(iii) 6020000000000000 = 6.02 × 10¹⁵
(iv) 0.00000000837
= \(\frac{837}{100000000000}\)
= \(\frac{8.37 \times 100}{10^{11}}\)
= 8.37 × 10^-12 × 10^-11
= 8.37 × 10^-9

(v) 31860000000 = 3.186 × 10¹⁰.

Question 2.
Express the fallowing number in 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:

= 361492 × 10^6-5
= 361492 × 10 = 3614920.

Question 3.
Express the number appearing in the following statements in standard form :
(i) 1 micron is equal to \(\frac{1}{1000000}\) m.
(ii) Charge of an electron is 0.000,000,000,000,000,000,16coulom b.
(iii) Size of a 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:

= 1.275 × 10^3-8
= 1.275 × 10^-5 m.
(v) Thickness of a thick paper
= \(\frac{7}{100}\) = \(\frac{7.0 \times 10}{10^{2}}\)
= 7.0 × 10^1-2
= 7.0 × 10^-1 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:
Total thickness of stack
= 20 m + 0.016
= 20.016
= \(\frac{20016}{1000}\) = \(\frac{2.0016×1000}{1000}\)
= \(\frac{2.0016 \times 10^{4}}{10^{3}}\)
= 2.0016 × 10.