Significant figures

What are significant figures?

microscope

They are the digits that 'count' or 'matter'
Consider for example if a microscope can measure with an accuracy of a hundredth and it measures that small object is 0.25 units. Well, that means that if we use this microscope's measurements in some other calculations then we never really can be more accurate than the hundredth place.

Examples
314 3 significant digits
310 3 significant digits
0314 3 signficant digits
304 3 significant digits
001 1 significant digit
200 2 significant digits
200 2 significant digits
Some Takeaways from the examples above:
  • leading zeros do not count (see examples 3 and 5)
  • If you have several trailing zeros like examples 6 and 7, then you can underline the last significant digit (example 7) OR you can overline it like example 6.

Significant Digits Less than 1, like .0015

You do not count the leading zero's.
So, there are 2 significant digits in .0015

Practice Problems

Number How many significant figures?
0.12
Two
0.012
Two
0.00120

4
We are using the overline notation to indicate that the final zero is indeed a significant digit.

300.0

4
Writing out the '.0' as a decimal point (instead of writing '300') implies that all digits are significant.
Therefore, all 4 digits are significant

300

2
Underlining the '0' is 1 of the ways to indicate that that digit is the last (or 'least' ) significant digit
Therefore, only 2 digits are significant.

300

1
You can only assume that the first digit. the '3' is significant.

toSignificant Figures Operations

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