1.1 Significant Figures (Part 2)

1.1 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)  8.608 ÷ 0.08 28.35
(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.)

(b)
0.062 × 30.12 + 1.268
= 1.86744 + 1.268
= 3.13544
= 3.14 (3 s. f.)

(c)
 
8.608 ÷ 0.08 28.35
= 107.6 – 28.35
= 79.25
= 79.3 (3 s. f.)

(d)
 
0.846 ÷ 0.4 0.153 × 2
= 2.115 – 0.306
= 1.809
= 1.81 (3 s. f.)



Example 1:
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
= 10.84
= 10.8 (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.)

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