A fact family is a group of facts made from the same three numbers. With 3, 5 and 8 we can write 3 + 5 = 8, 5 + 3 = 8, 8 − 5 = 3 and 8 − 3 = 5.
If you know one fact, you know the whole family. This helps you take away: to work out 12 − 7, think 7 + 5 = 12, so 12 − 7 = 5.
Worked example
Write the fact family for 4, 6 and 10.
- Two adding facts: 4 + 6 = 10 and 6 + 4 = 10.
- Two taking-away facts start with the biggest number.
Answer:10 − 6 = 4 and 10 − 4 = 6
Key words
- fact family
- facts that use the same three numbers
- whole
- the biggest number, the total
- part
- one of the two smaller numbers
Practise this
New questions every time.
Common Core-referenced: 1.OA.B.4