In this case, the number of

significant figures is determined by the number

of decimal places of the measurement that's

being either added or subtracted, that has

the least number of decimal places going in.

For example, let's take the number 52.369, which has 5 significant

figures, and add to that the number 69.2, which has 3 significant figures.

If we

just added up all those digits, we'd get an answer of 121.569.

Now the way I've written that answer, it

has, six significant figures, but really, I should draw

a line To the right of the least significant

digit which here is this two of the 69.2.

And that's how many decimal places the answer should have.

So the answer here should be to the tens place.

And it should have only one decimal place.

In other words, this answer should have four significant figures.

[NOISE] Let's do another example.

Let's take the number 0.2597 and subtract from that 0.034.

In this case I have a number with four significant figures.

And I'm subtracting from it a number that has only two

significant figures.