### Number of Sig Fig

Posted:

**Thu Oct 04, 2018 9:27 pm**Will there ever be a case where your answer contains less sig figs than there should be? And if so do you add a decimal point and trailing zeros? Or will this never happen?

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=9&t=33086

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Posted: **Thu Oct 04, 2018 9:27 pm**

Will there ever be a case where your answer contains less sig figs than there should be? And if so do you add a decimal point and trailing zeros? Or will this never happen?

Posted: **Thu Oct 04, 2018 9:34 pm**

The least number of sig figs in any number of the problem determines the number of significant figures in the answer. Trailing zeroes behind a decimal point will count as sig figs. For example, 6.48 / 2.16 = 3.00

Posted: **Thu Oct 04, 2018 11:11 pm**

The rule for trailings zeroes for sig figs can be a little misleading, but the best indicator is always the presence or absence of a decimal point. Lack of a decimal point can lead to uncertainty, but any time there is a decimal point, count the trailing zeroes regardless of whether they are before or after the decimal point.

Posted: **Thu Oct 04, 2018 11:19 pm**

When it comes to significant figures you always go by the least precise number. For example, 2.3 x 2.22 = 5.106. However, due to the least precise number being 2.3 you only have two significant figures. So, the answer would be 5.1. I have always been taught that the safest way to approach sig figs is by doing all of the calculations, keeping all of the numbers exact, and then once you have your final answer then you can apply significant figures.

Posted: **Thu Oct 04, 2018 11:33 pm**

So is it generally safe to not worry about sig figs in your calculations until you reach your final answer? When showing our work on tests do you think it'll be ok to use exact numbers until the end of the problem?

Posted: **Fri Oct 05, 2018 11:32 am**

Yes that is exactly what you should do so you don't get rounding errors!

Posted: **Fri Oct 05, 2018 11:59 am**

When calculating throughout the problem, only round to the proper amount of sigfigs at the very end of the problem, otherwise your answer will be significantly off than what it should be.

Posted: **Fri Oct 05, 2018 3:12 pm**

If there are multiple parts to one question, like part (a) and part (b), and when we want to calculate the answer for part (b), we need to use the answer from part (a), do we use the rounded off answer or the more accurate raw answer? Or are they both okay?

Posted: **Fri Oct 05, 2018 3:50 pm**

Given that you will be answering part a with a rounded answer for sig figs, I think it's fine to use that rounded answer in part b because your final answer for part b will ultimately be rounded for sig figs as well.