Check Addition With Subtraction

Check an Addition with Subtraction

Addition and subtraction are inverse operations. That means if you add two numbers to get a sum, you can use subtraction to check whether the sum is correct.

1. Start with the addition

Suppose you have:

a + b = s

To check it, subtract one addend from the sum.

2. Subtract one number from the sum

Use:

sum - addend = other addend

For example, if 7 + 5 = 12, check it by doing:

12 - 7 = 5

or

12 - 5 = 7

If the answer matches the other number in the addition, the sum is correct.

3. Use the check to confirm your work

If the subtraction gives the same addend you started with, your addition is verified. If it does not, the addition may contain an error.

4. Quick check method

• Identify the sum.
• Subtract one addend from it.
• See whether the result matches the other addend.

5. Final check

You can also check by reversing the subtraction: the difference and the subtracted number should add back to the original sum. This helps you be confident that your addition answer is correct.