Sig Figs... when to round?

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rosemarywang4i
Posts: 34
Joined: Fri Sep 28, 2018 12:28 am

Sig Figs... when to round?

Postby rosemarywang4i » Wed Oct 03, 2018 9:25 pm

I'm not quite sure when to round off my significant figures when doing a problem that has multiple mathematical steps. For example, question E1 asks firstly for the number of atoms in 1.00mol Ag and then to multiply that number by 144pm to get a final length. I understand that I would have to multiply 1.00mol by Avogadro's constant getting 6.0221e10^23 atoms, would I round to 3 sig figs there and then multiply by 144pm, or wait until the final step to round?

Shreya Tamatam 3B
Posts: 30
Joined: Fri Sep 28, 2018 12:25 am

Re: Sig Figs... when to round?

Postby Shreya Tamatam 3B » Wed Oct 03, 2018 9:33 pm

I believe you would round your final answer rather than rounding the numbers in earlier steps. This will make sure your final answer is more accurate. Wait until the final step to round!

Charles Gu 1D
Posts: 60
Joined: Fri Sep 28, 2018 12:16 am

Re: Sig Figs... when to round?

Postby Charles Gu 1D » Wed Oct 03, 2018 11:21 pm

I think you should maintain your rounding to the lowest number of sig figs that is given in the problem. For example, if the problem says there are 5.43 grams of Carbon and that is the lowest number of sig figs given in the problem, then your calculations should have 3 sig figs too.

Manya Kidambi 3I
Posts: 31
Joined: Fri Sep 28, 2018 12:24 am

Re: Sig Figs... when to round?

Postby Manya Kidambi 3I » Wed Oct 03, 2018 11:23 pm

To add on to what has already been said, it really helps if you store the value in your calculator as you are solving. That way, you get the most accurate answer. If you round as you go, your answer will probably be off by a few digits.

Courtney McHargue 1I
Posts: 56
Joined: Fri Sep 28, 2018 12:17 am

Re: Sig Figs... when to round?

Postby Courtney McHargue 1I » Thu Oct 04, 2018 1:00 pm

Never round off by sig figs in the middle of the problem, but keep in mind the sig figs of each new value you are continually using in a problem. At the end of the problem look at the supposed sig figs the values you used had and then round off to that number of sig figs.

Rachel Dang 1H
Posts: 32
Joined: Fri Sep 28, 2018 12:17 am

Re: Sig Figs... when to round?

Postby Rachel Dang 1H » Thu Oct 04, 2018 2:05 pm

If you round in between your answer could either be erroneously high or low (depending on whether or not you round up or down) and be off, so it's best to wait until the very end and keep all your number in your calculator if you can.

AdityaGuru1H
Posts: 65
Joined: Fri Sep 28, 2018 12:17 am

Re: Sig Figs... when to round?

Postby AdityaGuru1H » Thu Oct 04, 2018 3:52 pm

If we are not supposed to round until the end does it matter if we have the correct sig figs in each step of the problem or will the sig figs only matter at the end in regards to grading

Shuyi Yu 1B
Posts: 60
Joined: Fri Sep 28, 2018 12:16 am

Re: Sig Figs... when to round?

Postby Shuyi Yu 1B » Thu Oct 04, 2018 4:33 pm

For some of the homework problems I got answers that are off by a few numbers because of sig figs and rounding. Would my answers still be correct and what is the accepted range for the answers?


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