How to Check Your Subtraction Answers

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What is the opposite, or 'inverse', operation of subtraction?

Addition. You can use addition to check your subtraction work.

You solved $35 - 12 = 23$. How do you use addition to check this?

Add the number you subtracted ($12$) to your answer ($23$). If it equals the starting number ($35$), you're correct!

Let's check $35 - 12 = 23$. What is $23 + 12$?

$35$. Since $23 + 12 = 35$, the original subtraction was correct.

I solved $88 - 40 = 48$. What addition problem should I do to check my work?

$$48 + 40$$

What is $48 + 40$? Does this mean the answer to $88-40=48$ is correct?

$48 + 40 = 88$. Yes, the answer is correct.

Your answer for $76 - 25$ is $51$. Is this correct? Check with addition.

Yes, it's correct because $51 + 25 = 76$.

A friend says $67 - 15 = 42$. Check their answer using addition.

It's incorrect! $42 + 15 = 57$, not $67$. The correct answer is $52$.

If you solve a problem like (Big Number - Small Number = Answer), how do you check it?

You check if (Answer + Small Number = Big Number).

To check the problem $A - B = C$, what addition sentence do you write?

$$C + B = A$$

Use addition to check if this is correct: $99 - 81 = 18$.

Yes, it is correct. $18 + 81 = 99$.