Subtraction within ten
You learn to work out a subtraction by thinking of the addition that goes with it.
How to work it out
- Turn subtraction into addition: 9 − 5 becomes 5 + ? = 9.
- Find what completes the sum.
A worked example
9 − 5
- Turn it round: 5 + ? = 9.
- The missing number is 4, because 5 + 4 = 9.
- So 9 − 5 = 4.
More examples
8 − 3
- Turn it round: 3 + ? = 8.
- The missing number is 5, because 3 + 5 = 8.
- So 8 − 3 = 5.
10 − 7
- Turn it round: 7 + ? = 10.
- The missing number is 3, because 7 + 3 = 10.
- So 10 − 7 = 3.
7 − 2
- Turn it round: 2 + ? = 7.
- The missing number is 5, because 2 + 5 = 7.
- So 7 − 2 = 5.
Try it yourself
9 − 4 =
7 − 3 =
Watch out
You add the two numbers: for 9 − 5 you say 14.
Look at the sign. With a minus, the answer is smaller than the first number.
Tips
- Check your answer with an addition: 9 − 5 = 4, because 5 + 4 = 9.
- You can also count on from the small number to the big number.
Why it works
Addition and subtraction belong together: 5 + 4 = 9 also means 9 − 5 = 4. You probably know your additions to ten well already. If you turn the subtraction round, you use what you already know.