### E7

Posted:

**Thu Oct 05, 2017 7:47 pm**how do I know at what step in the problem to start rounding my sig figs to the given value?

Created by Dr. Laurence Lavelle

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

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=26&t=21904

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Posted: **Thu Oct 05, 2017 7:47 pm**

how do I know at what step in the problem to start rounding my sig figs to the given value?

Posted: **Thu Oct 05, 2017 8:43 pm**

I don't round my sig figs until the very end to prevent my answer from going too far off from the correct answer.

Posted: **Thu Oct 05, 2017 8:48 pm**

I agree. I don't start rounding off my sig figs until the very end when I receive the answer, to which I then correctly round the sig figs to. However, I am sure that even if you round your sig figs after every step, points will not be taken off for not having the most accurate answer.

Posted: **Thu Oct 05, 2017 9:44 pm**

Prof. Lavelle said that he isn't stressing sig figs as much as the content/information. Although, it's a better idea to round off at the end, because truncating your numbers too early can drastically change your answer.

Posted: **Thu Oct 05, 2017 10:46 pm**

It's best to round in the final step of the problem to avoid any rounding error.

Posted: **Thu Oct 05, 2017 11:27 pm**

How many sig figs is usually ideal for an answer? Should we truncate it to 3 digits or however many there are in the numbers given in the problem?

Posted: **Thu Oct 05, 2017 11:32 pm**

A TA and UA said to only round off to the number of sig figs you need at the very end of the problem, that way you can make the answer as accurate as possible. Also you're supposed to have as many sig figs in the answer as there are in the given numbers with the least sig figs. So for example, if you're given 2.5g of A and 355g of B and are asked to solve a problem, the answer should have just 2 sig figs (from the 2.5).

Posted: **Fri Oct 06, 2017 12:18 am**

In order to have the most precise and accurate answer, it is best to not round sig figs until the end once you have finished the problem. To figure out the number of sig figs you use, look at the number of sig figs used in the original problem.

Posted: **Fri Oct 06, 2017 2:48 pm**

The significant figures for the given value in the original question determine the number of significant figures that you should have in your answer, however hold off on rounding until the very end to be more accurate.

Posted: **Sat Oct 07, 2017 6:28 pm**

For that problem I rounded off to 3.487 but the textbook stopped at 3.5, which is the same as what the problem originally gave so I'm sure that's fine.