Subtraction with tens and ones
You learn to subtract tens and ones: first the tens, then the ones.
How to work it out
- Split the second number into tens and ones.
- Take away the tens first.
- Then take away the ones.
A worked example
76 − 28
- Partition 28 into 20 and 8.
- Take away the tens: 76 − 20 = 56.
- Take away the ones: 56 − 8 = 48.
More examples
93 − 27
- Partition 27 into 20 and 7.
- Take away the tens: 93 − 20 = 73.
- Take away the ones: 73 − 7 = 66.
64 − 34
- Partition 34 into 30 and 4.
- Take away the tens: 64 − 30 = 34.
- Take away the ones: 34 − 4 = 30.
Try it yourself
72 − 38 =
64 − 34 =
Watch out
You swap the ones round: for 76 − 28 you do 8 − 6 and say 52.
Take all 8 away from 56. If that crosses the ten, jump back to 50 first.
Tips
- Take away the tens first, because that is the biggest step.
- Check with an addition: 48 + 28 = 76, so 76 − 28 = 48.
Exceptions
- If the second step crosses the ten, like 56 − 8, jump back to 50 first.
Why it works
For 76 − 28 you partition 28 into 20 and 8. Taking away 20 first is easy: 76 becomes 56. Then you take away the 8, and you can bridge through the ten: 56 − 6 − 2.