Significant Figures II:
Significant Figures in a X or ÷ calculation.
The rule for significant figures in a multiplication or
division calculation is simple. Find the number in
the calculation with the LOWEST number of
significant figures.
The number of significant figures in your answer
MUST BE THE SAME!
Significant Figures II:
Significant Figures in a X or ÷ calculation.
Example 1:
32.1 ÷23.79 = 1.34931 (raw answer)
What is the correct answer with the appropriate
number of significant figures?
32.1 - 3 sig fig
23.79 – 4 sig fig
so my final answer should have 3 sig fig.
Rounding 1.34931 to 3 sig fig, I get:
1.35
Significant Figures II:
Significant Figures in a X or ÷ calculation.
Example 2:
.079 X 1056 = 83.424 (raw answer)
What is the correct answer with the appropriate
number of significant figures?
.079 - 2 sig fig
1056 – 4 sig fig
so my final answer should have 2 sig fig.
Rounding 83.424 to 2 sig fig, I get:
83
Significant Figures II:
Significant Figures in a X or ÷ calculation.
Example 3: Circumference of a circle = 2∏r
If r = 5.26 inches and ∏=3.1416
C = 2 X 3.1416 X 5.26 = 33.0496 in. (raw answer)
What is the correct answer with the appropriate
number of significant figures?
2 – infinite sig fig (counting number)
3.1416 – 5 sig fig
5.26 – 3 sig fig
so my final answer should have 3 sig fig.
Rounding 33.0496 to 3 sig fig, I get:
33.0 in
Significant Figures II:
Significant Figures in a X or ÷ calculation.
Work your way through the following practice
problems and answers.
Practice Problems
38.00 X .00798 = ?
.303
.30324 raw
38.00 – 4 sig fig
.00798 – 3 sig fig
so answer must be rounded to 3 sig fig
Practice Problems
2300 ÷ 100 = ?
20
23.00 raw
2300 – 2 sig fig
100 – 1 sig fig
so answer must be rounded to 1 sig fig!
Practice Problems
Surface area of a sphere with a radius of 2.0 inches
S=4∏R2 ( use 3.14 for ∏)
50. in2
50.240 raw
4 – exact number, infinite sig fig
3.14 – 3 sig fig
2.0 in – 2 sig fig
so answer must be rounded to 2 sig fig!
I include decimal in answer so 0 counts as sig fig