1.1.2 Significant Figures (Part 2)
1. Perform combined operations (addition, subtraction, multiplication and division) involving numbers, the final answer is rounded off to specific significant figures.
Example:
Find the value of each of the following and give your answer correct to 3 significant figures.
(a) 261.9 + 75.6 × 0.7
(b) 0.062 × 30.12 + 1.268
(c)
(d) 0.846 ÷ 0.4 - 0.153 × 2
Solution:
(b) 0.062 × 30.12 + 1.268
(c)
(d)
(d) 0.846 ÷ 0.4 - 0.153 × 2
Solution:
(a) 261.9 + 75.6 × 0.7
= 261.9 + 52.92
= 314.82
= 315 (3 s. f.)
= 315 (3 s. f.)
(b) 0.062 × 30.12 + 1.268
= 1.86744 + 1.268
= 3.13544
= 3.14 (3 s. f.)
(c)
= 107.6 – 28.35
= 79.25
= 79.3 (3 s. f.)
= 79.3 (3 s. f.)
(d)
= 2.115 – 0.306
= 1.809
= 1.81 (3 s. f.)
Example 1:
Solution:
Example 2:
Example 3:
Solution:
Calculate the value of 5.33 + 0.33 × 17 and give your answer correct to three significant figures.
Solution:
5.33 + 0.33 × 17
= 5.33 + 5.61
= 10.94
= 10.9 (3 s. f.)
Example 2:
Calculate the value of 49.3567 + 16.73 ÷ 0.5 and give your answer correct to four significant figures.
Solution:49.3567 + 16.73 ÷ 0.5
= 49.3567 + 33.46
= 82.8167
= 82.82 (4 s. f.)
Example 3:
Calculate the value of 3.42 ÷ 12 × 3.7 and give your answer correct to four significant figures.
Solution:
3.42 ÷ 12 × 3.7
= 1.0545
= 1.055 (4 s. f.)