Lesson 9: Addition and Subtraction

Property

To add or subtract decimals, align the numbers by their decimal points. Add or subtract as you would with whole numbers, starting from the rightmost digit. Place the decimal point in the answer directly below the decimal points in the numbers above.

Examples

• $145.78 + 92.3 = 238.08$
• $204.5 - 67.123 = 137.377$
• $89.654 + 11.47 = 101.124$

Explanation

When adding or subtracting larger decimal numbers, the process remains the same. The key is to carefully align the decimal points to ensure you are adding or subtracting corresponding place values. You can add trailing zeros to numbers to make them the same length after the decimal point, which can help with alignment. Then, simply perform the operation as if they were whole numbers and bring the decimal point straight down into your answer.