## Significant Figures involving constants

Alma Cruz 1A
Posts: 21
Joined: Fri Jun 23, 2017 11:40 am

### Significant Figures involving constants

When calculating problems involving constants such as the speed of light, do we use the number provided in the solutions manual (c=2.998x10^8) or the one provided in the list of equations and constants (c=2.99792x10^8)?

In other words, how do we know how many significant figures to correctly use and when to round?

Chem_Mod
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Joined: Thu Aug 04, 2011 1:53 pm
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### Re: Significant Figures involving constants

For homework problems use the constants with more significant figures.

Most of the time constants have more significant figures than the measured (given) values in the problem.
Therefore using a constant with 6 sig fig versus 4 sig fig is not that helpful when the calculation involves measured numbers with only 2 sig fig.

As I have typed several times this week:
Everyone is given the same constants and equations in all my tests and exams. Therefore in a test/exam everyone is using the same information (numbers).

Sheel Shah 1H
Posts: 33
Joined: Fri Sep 29, 2017 7:04 am

### Re: Significant Figures involving constants

I would use the one provided with list of equations, just because it has been measured to increased accuracy, and you may be expected to do the same.

I would also look for what other values in the question have been rounded off to. For example, if all the values in a question have 3 significant figures, use the 3 sig figs in your answer as well :)

- Sheel Shah