### How Many Sig Figs

Posted:

**Sun Oct 13, 2019 3:45 pm**On tests and exams, when the amount of significant figures we are supposed to round to is not listed, how many should we normally put the answer in?

Thank you.

Thank you.

Created by Dr. Laurence Lavelle

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

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=9&t=47238

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Posted: **Sun Oct 13, 2019 3:45 pm**

On tests and exams, when the amount of significant figures we are supposed to round to is not listed, how many should we normally put the answer in?

Thank you.

Thank you.

Posted: **Sun Oct 13, 2019 3:51 pm**

For addition, subtraction, multiplication, and division, the sig figs in the result should match the smallest amount of sig figs in the data or problem. For logs and exponentials, there should be the same number of sig figs in the problem and the result.

Hope this helps!

Hope this helps!

Posted: **Sun Oct 13, 2019 3:52 pm**

I'm pretty sure we just use the lowest amount of significant figures found in the numbers that are given to you already in the problem.

Posted: **Sun Oct 13, 2019 5:10 pm**

If that is the case, I would use decimal places to figure out rounding. Or, if you need to use the periodic table, use the sig figs of the molar masses to figure out the final sig fig value.

Posted: **Sun Oct 13, 2019 5:16 pm**

On Lavelle's main page of his website there is a document that answers a bunch of questions about sig figs. One thing I noticed that was important was in addition and subtraction go by the fewest number of decimal places. But in multiplication and division just the fewest number of sig figs

Posted: **Sun Oct 13, 2019 5:18 pm**

My TA said that we shouldn't be too worried about sig figs since they haven't really been specified. However, it's a general rule of thumb to use the amount of sig figs that the value with the least amount of sig figs in a problem has.

Posted: **Sun Oct 13, 2019 9:31 pm**

For addition use the number of decimal places and for multiplication use the lowest number of sig figs

Posted: **Sun Oct 13, 2019 9:44 pm**

You should follow the standard sig fig rules for multiplication/division and addition/subtraction. For addition/subtraction, the number of sig figs should match the smallest amount of decimals in a given value. For multiplication/division, the number of sig figs should match the smallest amount of sigs figs in a given value.