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Rounding Numbers to Significant Figures

 

After you finished your calculation, now it is time to round your answer to the determined number of sig. figs.

 

For numbers where you are cutting off  decimal places, round the sig. fig.  up if you are cutting off a 5 or greater.

Example

Rounding      120.4678   to 5 sig figs

==> 120.47
1,009.0467  to 6 sig figs ==>1,009.05
       0.004537 to   2 sig figs ==>0.0045

For numbers where you are cutting a non-decimal place, you must replace these numbers with zeros. You also must round the last sig. fig. up if you are cutting off a 5 or greater.

Examples       

Rounding     9,037 to 1 sig. fig.

==> 9,000
 12,354 to 3 sig. figs. ==>12,400
       1,235,752 to 2 sig. figs. ==>1,200,000

The full proof way to always round correctly is to use Scientific Notation. The number of digits in the mantissa is the number of sig. figs.

Example                       

Rounding     1,000,000 to 3 sig. figs.

==>1.00 x 106
  100 to 2 sig. figs. ==>1.0 x 102
       1,235,752 to 2 sig. figs. ==>1.2 x 106

Metric System  Metric conversions  Accuracy Precision Dimensional Analysis Scientific Notation  Significant Figures  Significant Figures in Calculations Rounding using Significant Figures Density

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