Who is this guide for?

It is written for readers who need a clear, practical explanation before taking action.

How often is this page updated?

The page can be regenerated or refreshed from the management interface when source data changes.

Home
Learning
subtraction
Checking subtraction with addition

subtraction

Checking subtraction with addition

Use inverse operations to check answers.

Quick answer

You can check if your subtraction is correct by adding the answer back to the number you took away. If you get the original number, your subtraction was right!

Learning outcome

By the end of this page, you will be able to check your subtraction answers using addition, so you know if your answer is correct. Success signs:

You can explain what inverse operations are
You can check a subtraction problem by adding
You can spot when a subtraction answer is wrong
You can use this method when solving maths problems

Why this matters

Checking your work helps you catch mistakes before they cause problems later. Whether you're solving puzzles, sharing snacks, or working out how many toys you have left, knowing how to double-check your maths helps you feel confident and sure of your answers. This skill also helps you understand how subtraction and addition are connected.

How it works

Subtraction and addition are connected through something called inverse operations. This means one operation "undoes" the other. When you subtract a number, you can add it back to see if you get the original number. Here's how it works step by step:

Start with a subtraction problem
Work out the answer to that subtraction
Add the number you subtracted to your answer
If the result matches your original number, your subtraction was correct

Examples you can see

Let’s look at a few examples to make this clearer. Example 1:

Subtraction: 10 - 3 = 7
Check: 7 + 3 = 10
Since 10 is the original number, the subtraction was correct!

Example 2:

Subtraction: 15 - 8 = 7
Check: 7 + 8 = 15
Since 15 is the original number, the subtraction was correct!

Example 3:

Subtraction: 20 - 5 = 15
Check: 15 + 5 = 20
Since 20 is the original number, the subtraction was correct!

Let’s try one more with a larger number: Example 4:

Subtraction: 42 - 18 = 24
Check: 24 + 18 = 42
Since 42 is the original number, the subtraction was correct!

Try it as a mini adventure

Adventure: The Treasure Hunt You are on a treasure hunt and have found a map with clues. The map says:

Start at the big tree.
Walk 12 steps forward.
Turn left and walk 5 steps.
You find a treasure chest with 12 gold coins.
You take 5 coins from the chest.
How many coins are left in the chest?

Now solve the subtraction:

12 - 5 = 7 coins left

Check your answer by adding:

7 + 5 = 12 coins

Great! You found the right number of coins. You can now open the treasure chest and take 7 coins home with you.

Common mistakes

Mistake: Forgetting to add the number you took away.
Why it happens: Kids might think they are done after subtracting, not realising they need to add back.
Fix: Always double-check that you add the number you subtracted to your answer.
Mistake: Adding the wrong number.
Why it happens: Confusion between the numbers in the problem.
Fix: Look carefully at your subtraction problem and make sure you add back the correct number.
Mistake: Thinking subtraction and addition are unrelated.
Why it happens: Not understanding that one "undoes" the other.
Fix: Remember that subtraction and addition are partners in maths.

Parent and carer guide

Parents and carers can help by:

Repeating the idea of inverse operations with simple examples
Practising the check method with your child using small numbers
Encouraging your child to say "I'll add back to check" when solving subtraction problems
Using real-life situations like sharing snacks or counting toys to make the concept clear
Noticing if your child skips the checking step and gently reminding them

When your child is learning, it's normal to make mistakes. The key is to help them understand why they made the mistake and how to fix it. If your child gets confused, try to use objects or drawings to show how the numbers work together.

Practice questions

Subtraction: 10 - 4 = 6. Check: 6 + 4 = ?
Subtraction: 18 - 9 = 9. Check: 9 + 9 = ?
Subtraction: 25 - 12 = 13. Check: 13 + 12 = ?
Subtraction: 30 - 15 = 15. Check: 15 + 15 = ?
Subtraction: 45 - 20 = 25. Check: 25 + 20 = ?

Answers:

6 + 4 = 10
9 + 9 = 18
13 + 12 = 25
15 + 15 = 30
25 + 20 = 45

FAQ

What is an inverse operation?

An inverse operation is a maths operation that "undoes" another operation. For example, subtraction and addition are inverse operations.

Why do we check subtraction with addition?

We check subtraction with addition to make sure our answer is correct. It helps us catch any mistakes.

Can I check subtraction with other methods?

Yes, you can also check by counting backwards or using a number line, but checking with addition is the quickest and easiest way.

Is checking subtraction important?

Yes, checking your work helps you build confidence and ensures you get the right answer in tests, games, and everyday life.

What if my subtraction answer is wrong?

If your answer doesn’t add up correctly, go back and recheck your subtraction. You can try it again or ask someone to help you.