Fact Families to 20

What a fact family is

A fact family uses the same three numbers to make four related equations: two additions and two subtractions. The numbers stay the same, but their order changes.

How to write the four facts

1. Identify the three numbers. Usually two smaller numbers add to a larger number.
2. Write the two addition facts:
   • smaller + smaller = larger
   • the same numbers in the other order
3. Write the two subtraction facts:
   • larger − first smaller = second smaller
   • larger − second smaller = first smaller

Example

If the three numbers are 3, 5, and 8:

• 3 + 5 = 8
• 5 + 3 = 8
• 8 − 3 = 5
• 8 − 5 = 3

Check your work

Make sure every equation uses only the same three numbers. In the subtraction facts, the answer should be one of the smaller numbers, and the number you subtract from should be the largest number. If you can turn each addition into a matching subtraction, your fact family is correct.