In multiplying or dividing measurements, how should you round the result?

• A. The least number of decimal places
• B. The most precise measurement
• C. The fewest total digits
• D. The least number of significant figures

Answer: (D)

The key idea is that precision in multiplication or division is limited by the least precise measurement involved. When you multiply or divide numbers, the final result should be reported with the same number of significant figures as the input with the fewest significant figures. This keeps the reported precision honest to what the data actually supports.

For example, multiply 3.0 (two significant figures) by 2.50 (three significant figures). The exact product is 7.50, but since the limiting measurement has two significant figures, you round the result to two significant figures, giving 7.5. This rule ensures you don’t imply more certainty than your measurements justify. Note that this approach is specific to multiplication and division; rounding by decimal places is the guideline used for addition and subtraction.