# Significant Figures

## Homework Statement

The length of a cylinder is 1.2 x 10^-2 m and its radius is 2.12 x 10^-2 m. What is its volume according to significicant figures?

## The Attempt at a Solution

V=(pi)r^2 l
r^2 = 4.49 x 10^-4 (as radius has 3 significant digits)
V= 22/7 x 4.49 x 10^-4 x 1.2 x 10^-2
V= 22/7 x 5.4 x 10^-6 [4.49 x 10^-4 x 1.2 x 10^-2 = 5.388 x 10^-6 = 5.4 x 10^-6 as least no. of significant digits is 2 here)
so V=1.7 x 10^-5

Borek
Mentor
1.7x10-5 m3 looks correct to me. But you should not use 22/7 for pi nor round down intermediate results.

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Intermediate results have to be rounded off in order to satisfy the rules of significant figures.

Borek
Mentor
No. You should round them down only if you are displaying them, but you do the calculations using full accuracy.

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you mean to say that
5.388 x 10^-6 = 5.4 x 10^-6
should be written as 5.3 x 10^-6 ?

Borek
Mentor
No, when displaying it should be written as 5.4x10-5, but for calculations you should use 5.388x10-5.

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