Complete the fact family
To complete a fact family, find the three numbers, then write two facts that combine the smaller numbers and two that start with the biggest. For 5, 5 and 10: 5 + 5 = 10 and 10 − 5 = 5.
To complete a fact family, find the three numbers, then write two facts that join the two smaller numbers and two facts that start with the biggest number. For 5, 5 and 10 you write 5 + 5 = 10 and 10 − 5 = 5. This page shows how to answer the most common homework prompts, with practice you can check straight away.
How to complete a fact family
- Find the biggest number. It is the whole (or the product).
- Write the two facts that combine the smaller numbers: 5 + 5 = 10.
- Write the two facts that start with the biggest number: 10 − 5 = 5.
- If the two smaller numbers are the same, you only need two facts.
Check your family with the calculator
Complete the fact family: check your answer
Type any two numbers. The third number and all the facts appear.
- 5 + 5 = 10
- 10 − 5 = 5
Common homework prompts and how to answer them
“Complete each family of facts”
You are given three numbers, such as 3, 8 and 11, and a set of unfinished equations. Fill in each gap using only those numbers: 3 + 8 = 11, 8 + 3 = 11, 11 − 3 = 8, 11 − 8 = 3.
“Write the fact family for”
Write every fact. For 4, 6 and 24: 4 × 6 = 24, 6 × 4 = 24, 24 ÷ 4 = 6 and 24 ÷ 6 = 4.
“Write a related fact”
Use the same three numbers. A related fact for 9 + 4 = 13 is 13 − 4 = 9. See related facts.
“Find the missing number”
For 7 + ? = 16, use the fact family: 16 − 7 = 9, so the missing number is 9.
“How can a fact family help you subtract?”
Every subtraction fact is linked to an addition fact. To solve 16 − 7, think “7 plus what is 16?” You know 7 + 9 = 16, so 16 − 7 = 9. The fact family lets you turn a subtraction problem into an addition problem.
Try some
Complete the family: 6, 7, 13
6 + 7 = 13, 7 + 6 = 13, 13 − 6 = 7 and 13 − 7 = 6.
Complete the family: 8, 3, 24
8 × 3 = 24, 3 × 8 = 24, 24 ÷ 8 = 3 and 24 ÷ 3 = 8.
Complete the family: 9, 9, 18 (hint: only two facts)
9 + 9 = 18 and 18 − 9 = 9.
Complete: 15, 6 and ? (addition family)
The biggest given number is 15, so it is the whole. The other part is 15 − 6 = 9. Facts: 6 + 9 = 15, 9 + 6 = 15, 15 − 6 = 9 and 15 − 9 = 6.
Practice in the game
Practice: complete the fact family triangle
Print more problems
Choose Complete each family of facts in the worksheet maker to print as many problems as you like, with an answer key.