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Significant Figures

Significant figures:

All nonzero numbers
Zeros surrounded by nonzero numbers
zeros to the right of the decimal, and the last digit
zeros left of the decimal when the number is greater than 10

For adding and subtracting, answer will have the same number of digits past the decimal as the input number with the smallest amount

For multiplication and division, the answer will have the same number of sig figs as the input number with the smallest amount. Round when needed.

Examples

Number	Significant figures
23	2
303	3
12.0	3
100.0	4
5600	2
5600.0	5

What is the area of a circle with d=2.47m?
A= $\pi r^2$
A=(3.14)(1.235m) $^2$
A=4.7892m $^2$
A=4.79m $^2$
d has 3 sig figs $/pi$ has 3 sig figs
d= $2 \cdot r$
r= $\frac{2.48m}{2}$
r=1.235m