Exponents and Power
Exercise 12.2
Question 1: Express the following numbers in standard form
(a) 0.0000000000085
Answer: 8.5 × 10-12
(b) 0.00000000000942
Answer: 9.42 × 10-12
(c) 6020000000000000
Answer: 6.02 × 1015
(d) 0.00000000837
Answer: 8.37 × 10-9
(e) 31860000000
Answer: 3.186 × 1010
Question 2: Express the following numbers in usual form
(a) 3.02 × 10-6
Answer: 0.00000302
(b) 4.5 × 104
Answer: 45000
(c) 3× 10-8
Answer: 0.000000003
(d) 1.0001× 106
Answer: 1000100
(e) 5.8× 1012
Answer: 5800000000000
(f) 3.61492 × 106
Answer: 3614920
Question 3: Express the number appearing in the following statements in standard form
(a) 1 micron is equal to `1/(1000000) m
Answer: 1 × 10-6 m
(b) Charge of an electron is 0.000, 000, 000, 000, 000, 000, 16 coulomb
Answer: 1.6 × 10-19
(c) Size of a bacterium is 0.0000005 m
Answer: 5 × 10-7 m
(d) Size of a plant cell is 0.00001275 m
Answer: 1.275 × 10-5
(e) Thickness of a thick paper is 0.07 mm
Answer: 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?
Answer: Total thickness of 5 books = 20 × 5 = 100 mm
Thickness of 5 sheets = 0.016 × 5 = 0.08 mm
Total = 100 + 0.08 = 100.08 mm
= 1.0008 × 10-2