How to Teach Subtraction

1Why is it important?

Subtraction is needed every day, working out change at the store, knowing how much is left to reach a goal, or finding the difference between two numbers. It is also the mirror image of addition, and a child who understands the link between them saves half the work. The big hurdle in subtraction is borrowing, and a child who truly understands it stops being afraid of large numbers. It is worth investing here, because strong subtraction is a requirement for long division and the more complex work that comes later.

2How to teach?

• Start with a physical demonstration: there were 7 apples, we ate 3, how many are left?
• Explain that subtraction means taking away, and that the result is always smaller than the number you started with.
• Show the link to addition, since if 3 + 4 = 7 then 7 - 4 = 3, the same story told backwards.
• When you reach borrowing, explain it through tens and units, borrowing one ten and turning it into ten units.
• Practice subtraction without borrowing first, and only move to borrowing once that feels solid.

3Detailed examples

4Common mistakes

• Always subtracting the smaller digit from the larger one, even when borrowing is needed, so 53 - 27 wrongly becomes 34.
• Forgetting the borrow, and not taking 1 away from the tens digit after borrowing from it.
• Getting the order mixed up and trying to subtract the larger number from the smaller one, since subtraction is not reversible like addition.
• Getting stuck borrowing through zeros, as in 100 minus a number, where you have to borrow several times.

5Tips for parents

• Use games: you had 10 points and lost 3, how many are left now?
• Practice with money, since working out change is concrete and genuinely interesting to a child.
• If your child gets confused with borrowing, go back to blocks for tens and units and physically break a ten into ten.
• Remind them to check with addition: if 53 - 27 = 26, then 26 + 27 must come back to 53.
• Give it time, because borrowing has several steps, and speed only comes once the understanding is steady.