Significant Figures

  • Thread starter zorro
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  • #1
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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?

Homework Equations





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

Answer is 16.9 x 10^-6
 

Answers and Replies

  • #2
Borek
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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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  • #3
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Intermediate results have to be rounded off in order to satisfy the rules of significant figures.
 
  • #4
Borek
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No. You should round them down only if you are displaying them, but you do the calculations using full accuracy.

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  • #5
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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 ?
 
  • #6
Borek
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No, when displaying it should be written as 5.4x10-5, but for calculations you should use 5.388x10-5.

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