When making calculations in science, it is important to express the answer with the correct number of significant figures. In this section, you will look at the rules for calculations and significant figures.

Addition and Subtraction with Significant Figures

The rule for addition and subtraction with significant figures is as follows:

When adding and subtracting measurements, the level of accuracy at which you express your final answer does not depend on the number of significant figures in the original problem but instead is determined by the position or place value of the least significant digit in the original problem.

Watch the following video to see examples of adding and subtracting with significant figures.

Now you try! Remember,

1. complete the calculation as you normally would, and
2. express the final answer by rounding to the place value corresponding to the number in the original problem with the least accurate place value.

Multiplication and Division with Significant Figures

The rule for multiplication and division with significant figures is as follows:

This rule simply means the final answer can be no more accurate than the least accurate measurement. Count the significant figures in each measurement instead of the number of decimal places when multiplying and dividing measurements.

Watch the following video to learn more about multiplying and dividing with significant figures.

Now you try! Remember,

1. perform the calculation,
2. count the number of significant figures in each measurement, and
3. round the final answer using the least number of significant digits from the original problem.