Rounding

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April Meza 3K
Posts: 66
Joined: Sat Sep 21, 2019 12:36 am

Rounding

Postby April Meza 3K » Thu Oct 03, 2019 7:27 pm

How do I know when I need to round? For instance, if I were to use Lithium, which is 6.94, would it be that exact number or can I round to 7?

AKhanna_3H
Posts: 87
Joined: Wed Sep 18, 2019 12:19 am

Re: Rounding

Postby AKhanna_3H » Thu Oct 03, 2019 7:31 pm

In general, you would use the full number and then round to the correct number of significant figures as the last step of your calculations to get your final answer. For the most accuracy, avoid rounding any numbers in your calculations until the final answer.

April Meza 3K
Posts: 66
Joined: Sat Sep 21, 2019 12:36 am

Re: Rounding

Postby April Meza 3K » Thu Oct 03, 2019 7:33 pm

Okay, thank you!

Abbey Brandt 1K
Posts: 33
Joined: Fri Sep 28, 2018 12:29 am

Re: Rounding

Postby Abbey Brandt 1K » Thu Oct 03, 2019 7:59 pm

The best rule I can give you is to use the least specific number of sig figs used in the question itself. For example, if in the equation there are measurements including the digits 4.98, 5.667, and 0.2, you would use 1 significant figure. Does that help?

April Meza 3K
Posts: 66
Joined: Sat Sep 21, 2019 12:36 am

Re: Rounding

Postby April Meza 3K » Thu Oct 03, 2019 8:10 pm

Abbey Brandt 4E wrote:The best rule I can give you is to use the least specific number of sig figs used in the question itself. For example, if in the equation there are measurements including the digits 4.98, 5.667, and 0.2, you would use 1 significant figure. Does that help?


Yes, it does. Thanks!

805291863
Posts: 85
Joined: Sat Sep 14, 2019 12:16 am

Re: Rounding

Postby 805291863 » Thu Oct 03, 2019 9:13 pm

What I do is I use one more digit that the number of significant digits in the given values during all my calculations. At the very, I round my answer to the appropriate number of significant digits.

Matt F
Posts: 85
Joined: Sat Aug 17, 2019 12:17 am

Re: Rounding

Postby Matt F » Fri Oct 04, 2019 10:40 am

I generally round out to 2 or 3 decimal places, depending on the numbers given in the problem like those above me mentioned. You should be fine as long as you aren't rounding egregiously (Ex: rounding 16.53 to 17 for atomic weight). It also depends on context though. I typically wouldn't round like the example I gave, but for something like getting the empirical formula, you can more readily round to whole numbers.

Eva Zhao 4I
Posts: 86
Joined: Sun Sep 29, 2019 12:16 am

Re: Rounding

Postby Eva Zhao 4I » Fri Oct 04, 2019 3:54 pm

It's best to only round at the end of the calculations. If you round throughout the series of calculations, the answer could be different depending on the number of significant figures needed. Generally speaking, using 7 instead of 6.94 for Lithium can likely get you the right answer for say multiple choice questions. However, you should try to be as accurate as possible.

Karina Kong 2H
Posts: 84
Joined: Thu Jul 25, 2019 12:16 am

Re: Rounding

Postby Karina Kong 2H » Sat Oct 05, 2019 5:19 pm

It is best to try and not round until the end, otherwise it could offset your value by a few decimal points. Once you reach the end, round to the least amount of significant figures in the problem.

Ruth Glauber 1C
Posts: 85
Joined: Wed Sep 18, 2019 12:20 am

Re: Rounding

Postby Ruth Glauber 1C » Sat Oct 05, 2019 5:36 pm

I think it is best to round to the number of significant figures stated in the question (i.e. the number of sig figs of the data the question gives you).

Jessa Maheras 4F
Posts: 78
Joined: Fri Aug 02, 2019 12:16 am

Re: Rounding

Postby Jessa Maheras 4F » Sat Oct 05, 2019 6:39 pm

Along with some of the other good answers, it's important to remember to round to the correct number of Significant figures! Keeping in mind of course, the different rules for adding/subtracting and for multiplying/dividing.

Jasmine Kim 1L
Posts: 56
Joined: Fri Aug 02, 2019 12:16 am

Re: Rounding

Postby Jasmine Kim 1L » Sun Oct 06, 2019 11:41 pm

This is what I found in Appendix 1 (1C) of the textbook:
For addition and subtraction, you round to the lowest number of digits after the decimal.
For multiplication and division, you round to the smallest number of sig figs in general.
If there is a 0 right after the decimal and nothing after, like 3.0, then it counts as a sig fig. However, if it is a whole number, like 300, then it can be considered to have only 1 sig fig unless there is a decimal after (300. has 3 sig figs) or scientific notation is used (3.0 x 10^2 has 2 sig figs).

Katherine Brenner 3H
Posts: 73
Joined: Wed Sep 18, 2019 12:18 am

Re: Rounding

Postby Katherine Brenner 3H » Tue Oct 08, 2019 8:50 am

The number of significant figs in the question is the amount we are supposed to be using in our answer. For example if the question has 1.34 grams co2 then our answer should be 3 sig figs such as 8.23 x 10^28


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