These problems will help you master the rule for rounding answers to the correct number of decimal places when adding or subtracting measurements.

Practice Problems

Solve these problems and round your final answers to the correct number of significant figures. Check your answers using the Answer Key at the bottom of the page.

Problem 1: Simple Addition

A person walks 2.34 meters, then turns and walks another 5.1 meters. What is the total distance they walked?

Problem 2: Simple Subtraction

A piece of metal has an initial mass of 15.67 grams. A small piece is cut off, and the remaining mass is 2.1 grams less. What is the new mass of the metal?

Problem 3: Adding with Different Precision

A bottle of soda contains 0.355 liters. If you add 1.2 liters of water, what is the new total volume?

Problem 4: Subtracting with Different Precision

The initial temperature of a liquid is 250 degrees Celsius. After a chemical reaction, the temperature drops by 15.2 degrees. What is the final temperature?

Problem 5: Adding Multiple Numbers

Calculate the total mass of three objects with the following masses: 9.123 kg, 4.5 kg, and 10.0 kg.

Problem 6: Mixed Precision

A student measures the length of a desk as 1.50 meters. They then add a stack of books with a height of 0.2 meters. What is the new total height?

Show Answer Key

Problem 1: $7.4 \text{ m}$ (The least number of decimal places is 1, from 5.1 m).

Problem 2: $13.6 \text{ g}$ (The least number of decimal places is 1, from 2.1 g).

Problem 3: $1.6 \text{ L}$ (The least number of decimal places is 1, from 1.2 L).

Problem 4: $235 \text{ °C}$ (The least number of decimal places is 0, from 250 °C).

Problem 5: $23.6 \text{ kg}$ (The least number of decimal places is 1, from 4.5 kg and 10.0 kg).

Problem 6: $1.7 \text{ m}$ (The least number of decimal places is 1, from 0.2 m).

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