Sig Fig Rules

[Liliana Teitell]

I am pretty confused on what all the rules are for sig fig. I know that every number that isn't zero is significant, but what are the other rules? I'm confused on how I know whether a number is a sig fig.

[hollyf]

Sig Fig Rules:
1. All non-zero numbers are significant
2. zeros between two non-zero numbers are significant
3. leading zeros are not significant
4. trailing zeros to the right of the decimal are significant
5. trailing zeros in a whole number with the decimal shown are significant
6. trailing zeros in a whole number with no decimal shown are not significant
6. exact numbers have an infinite number of sig figs
7. for a number in scientific notation, all digits comprising 'N' are significant by the first 6 rules

[Liliana Teitell]

How do I know how many sig figs I should use?

[sadie_remillard_1A]

Hi Liliana,
Sig figs are quite tricky, so here's some other rules to follow besides the ones listed previously!
When adding/subtracting numbers together, the number with the least decimal places is called the "limiting term" and that is what you will base your sig figs on. For example: 6.22 (hundredths decimal place) + 53.6 (tenths decimal place) + 14.311 (thousandths decimal place) = 74.131 (w/out sig figs) --> 74.1 (w/ sig figs), because 53.6 only went to the tenth's place, it is the "limiting term" and thus you only go to the tenths place in your answer.
As for multiplying/dividing, your answer as a WHOLE should have the SAME number of sig figs as the "limiting term" (limiting term here means the number with the lease amount of significant figures) . For example: 503.29 (5 sig figs) x 6.177 (4 sig figs) = 3108.82233 (w/out sig figs) --> 3109 (w/ correct sig figs).

Other examples:
1. 3985 has 4 sig figs (all non-zero numbers)
2. 100045 has 6 sig figs (the zeros here are significant because they are between two non-zero numbers
3. 0.3 has 1 sig fig (the leading zero is not significant)
4. 100. has 3 sig figs (the zeros after the leading non-zero number are significant because there is a decimal point)

[Liliana Teitell]

Your explanation helps me so much. Thank you!!!!