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Check addition with subtraction

Addition can be checked using subtraction because the sum and the two addends form a related whole-part relationship: if a+b=ca+b=c, then c−a=bc-a=b and c−b=ac-b=a. This reasoning applies to whole-number equations within 1,000, using place-value understanding and part–whole representations, and supports solving missing-addend problems; it does not include negative numbers, decimals, or formal algebraic generalization.

Detailed Explanation: Check addition with subtraction

When you add two numbers, the answer is the whole, and the two numbers you added are its parts. You can check the addition by subtracting one part from the whole. The answer should be the other part.

Example:

236+148=384236+148=384

Here, 384384 is the whole, and 236236 and 148148 are the parts.

Check by subtracting 236236 from 384384:

384−236384-236
  • Ones: 44 cannot subtract 66, so regroup 1 ten as 10 ones. Then 14−6=814-6=8.
  • Tens: There are now 7 tens. 7−3=47-3=4.
  • Hundreds: 3−2=13-2=1.

So,

384−236=148384-236=148

The subtraction gives the other addend, 148148. This shows that the addition is correct.

You can also check the other way:

384−148=236384-148=236

Because both subtractions give the other addend, the equation

236+148=384236+148=384

is checked.

Learn by doing: Check addition with subtraction

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    Addition - Missing Value, 3 Digit, 2 Numbers

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