# What is the sum of 334.540 g and 198.9916 g to the correct significant figure?

##### 1 Answer
Jul 20, 2016

$533.532 \text{ g}$.

#### Explanation:

The rule for adding or subtracting numbers with finitely many significant digits is:

1) Find the lowest power of 10 place value with significant digits in both terms

2) Round the sum or difference to that power of 10.

So:

1) The number $335.540$ has significant digits down to a place.value of ${10}^{- 3}$ (three places past the decimal point); a terminal zero after a decimal point is considered a significant digit. The number $198.9916$ has significant digits down to the ${10}^{- 4}$ place but the other term does not match that.

2) So round your sum to a multiple of ${10}^{- 3}$, keep three digits to the right of the decimal point.

Thus $334.540 + 198.9916 = 533.5316 = \textcolor{b l u e}{533.532}$.