Whole-number subtraction can be checked by using addition as its inverse: if , then must equal , reconstructing the minuend from the difference and subtrahend. This relationship applies to equations and problems with nonnegative whole numbers through 1,000, including regrouping, and clarifies that the order and roles of the numbers matter; negative numbers, decimals, and generalized algebraic verification are beyond this scope.
To check a subtraction problem, use addition.
If
then check by adding the difference and the subtrahend:
The answer should equal the minuend, the number you started with.
Example:
Check the answer:
The sum is , which matches the minuend in the subtraction problem. Therefore,
is correct.
Remember: add the answer and the number you subtracted. Their sum should be the number you started with.
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