Consider three masses that you wish to add together: 3 g. 1.4 g, and 3.3 g. These numbers represent measured values. How do you add the numbers together and report your answer to the correct number of significant figures?

1 Answer
Meave60
Sep 2, 2016

The answer is #"8 g"#.

Explanation:

When adding or subtracting, the result should be rounded to the same number of decimal places as the number in the problem with the fewest decimal places.

#"3 g"+"1.4 g"+"3.3 g"="7.7 g"#

However, #"3 g"# is a whole number with no decimal places, so #"7.7 g"# should be rounded to the whole number #8#.

Therefore, #"3 g"+"1.4 g"+"3.3 g"="8 g"#

This illustrates the importance of recording measurements so that you record what you can read exactly from the instrument, plus one estimated digit.

For more information and practice, go to the following website.
http://www.chemteam.info/SigFigs/SigFigMath-AddSub.html

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