➕ Operations & Algebraic Thinking
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Fact Families

Addition and subtraction facts are related — they live in the same family!

A FACT FAMILY is a set of related addition and subtraction equations that all use the same three numbers. If you know one fact in the family, you can figure out all the others instantly!

🏠Fact family for 3, 5, and 8
The three numbers are: 3, 5, 8

Addition facts:
  3 + 5 = 8
  5 + 3 = 8

Subtraction facts:
  8 − 3 = 5
  8 − 5 = 3

All 4 facts belong to the same family!
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The BIGGEST number is always the sum (in addition) and the starting number (in subtraction).

How to write a fact family:

1Start with 3 numbers where two add up to the third (e.g., 4, 6, 10)
2Write 2 addition facts: 4+6=10 and 6+4=10
3Write 2 subtraction facts: 10−4=6 and 10−6=4
4Check: your biggest number should appear in all 4 facts!

Addition facts

4 + 7 = 117 + 4 = 11

Subtraction facts

11 − 4 = 711 − 7 = 4

Same three numbers (4, 7, 11) — four different facts. That's a fact family!

✏️ Try It!

The fact family uses 7, 4, and 11. Which is a correct fact from this family?

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Remember This!

Knowing one fact means knowing three more for free! If you remember 6 + 9 = 15, you also know 9 + 6 = 15, 15 − 6 = 9, and 15 − 9 = 6.

Take Quiz 📝 — 24 Questions