How it works
Numbers come in families. If you know 7 + 8 = 15, you also know 8 + 7 = 15, 15 − 7 = 8 and 15 − 8 = 7.
Make a ten to help: 8 + 5 is 8 + 2 to reach ten, then 3 more.
The more you practise, the more facts you know by heart.
Worked examples
A missing part
- 7 + ? = 15
- The whole and one part are given. Think of the partner that makes the whole.
- Use a fact you know, or make a ten.
- So the answer is 8.
A take-away fact
- ? = 12 − 8
- Turn it round: what must I add to the small number to reach the big one?
- That missing number is the answer.
- So the answer is 4.
A fact with a hidden answer
- 5 − 1 = ?
- Say the fact family out loud.
- One of its four facts has the answer in it.
- So the answer is 4.
A taste of the worksheet
These are the first problems of set A. The printable sheet has many more, with an answer key.
- 4 + 4 = __
- 2 + 2 = __
- 11 − 6 = __
- 5 − 2 = __
- __ = 5 + 5