### knowing how many sig figs to use

Posted:

**Thu Oct 03, 2019 12:32 pm**If a problem uses a certain amount of sig figs, should all our work use that amount of sig figs, or should we round to the sig fig amount only for the answer?

Created by Dr. Laurence Lavelle

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

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=8&t=46064

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Posted: **Thu Oct 03, 2019 12:32 pm**

If a problem uses a certain amount of sig figs, should all our work use that amount of sig figs, or should we round to the sig fig amount only for the answer?

Posted: **Thu Oct 03, 2019 12:48 pm**

You can use different amounts of sig figs as you're working on the problem, however make sure you keep track of how many sig figs for your final calculation. If you are constantly rounding to 3 sig figs, for example, it is probable your answer may be inaccurate or far from the actual answer.

Posted: **Thu Oct 03, 2019 2:43 pm**

I would suggest rounding to the correct amount of sig figs for the final answer and trying to keep the precise values on your calculator as you work through the problem, that way there is more accuracy.

Posted: **Thu Oct 03, 2019 3:01 pm**

I remember in class him saying not to round till the very last step but in showing work he would round in the lecture slides to neatly show the steps since the focus in the recent lectures were not actual sig figs. I suggest doing this on homework as well

Posted: **Thu Oct 03, 2019 3:07 pm**

I think in order to make your answers as accurate as possible, you shouldn't round to the correct number of significant digits until the very end. If you round with every step, your answer will gradually get farther and farther away from the actual answer, so I would say keep as many digits as possible until you reach the end of the problem. Then, pay attention to the number of sigfigs.

Posted: **Sat Oct 12, 2019 12:56 am**

To keep your work as accurate as possible, try not to round until the final answer. On the basis that you do round, keeping a certain number of significant figures should be enough to result in the final answer. For example, if the answer needs to have two significant figures, keeping four significant figures throughout your work will likely be enough (instead of maintaining, say, ten significant figures throughout).

Posted: **Sat Oct 12, 2019 10:41 am**

I would say when you are working on intermediate calculations, then have more numbers and at the end round to correct number because if you round to close in the intermediate calculations that can affect your final answer by a lot.

Posted: **Sun Oct 13, 2019 3:12 pm**

Does anyone know how much sig fig answers are worth in the context of tests and exams? How many points will be deducted if sig figs are used incorrectly?

Posted: **Sun Oct 13, 2019 3:15 pm**

You should keep as many sig figs as possible while you work on the problem in order to be the most accurate. Then at the end, you can round to the correct number!

Posted: **Sun Oct 13, 2019 3:19 pm**

I would recommend only rounding to the correct amount of sig figs when you reach your final answer. I would keep the exact value when doing calculations.

Posted: **Sun Oct 13, 2019 7:58 pm**

Eva Zhao 3B wrote:To keep your work as accurate as possible, try not to round until the final answer. On the basis that you do round, keeping a certain number of significant figures should be enough to result in the final answer. For example, if the answer needs to have two significant figures, keeping four significant figures throughout your work will likely be enough (instead of maintaining, say, ten significant figures throughout).

Thank you, I've been confused about this.

Posted: **Sun Oct 13, 2019 8:02 pm**

I was recommended to keep as many digits as possible until the very end. This last test, our TA told us that he wasn't placing a heavy emphasis on sig figs so we shouldn't worry about it, but they might start counting it in the future.

Posted: **Sun Oct 13, 2019 8:07 pm**

I think that it is proper to use the same amount of sig figs throughout the entire problem, so that there is consistency with each preceding calculation. Especially with given units, the sig figs in your final answer should likely match the amount of sig figs with these given numbers.

Posted: **Sun Oct 13, 2019 8:30 pm**

Is it usually safe to have four decimal places for calculations and answers?

Posted: **Sun Oct 13, 2019 8:33 pm**

You want to match the number of decimal places that correlates to the correct number of significant figures.

Posted: **Sun Oct 13, 2019 8:33 pm**

For calculations you may use as many decimal places as you see fit to be accurate but its good to use your answer in the least number of sig figs in the question.

Posted: **Sun Oct 13, 2019 8:35 pm**

Aman Sankineni 3E wrote:Is it usually safe to have four decimal places for calculations and answers?

For calculations I usually round to the nearest thousandth but once I get to the answer I make sure to match its sig figs to the # of sig figs used in the question :) I don't know if/how many points are taken off if we don't round the answer to the correct number of sig figs though :/

Posted: **Sun Oct 13, 2019 8:51 pm**

Sig Figs are important and you should keep them in mind while you're doing a problem but only round at the end