Definition
Fact family
A fact family is a group of related equations using the same numbers and inverse operations.
What it means
The equations belong together because each one tells the same number relationship from a different direction. Knowing one fact lets you turn it around or undo it with the inverse operation to find the others.
Remember it
Same numbers, related equations: turn the fact around or undo it.
Example
The numbers 4, 6, and 24 make this multiplication–division family: 4 × 6 = 24, 6 × 4 = 24, 24 ÷ 6 = 4, and 24 ÷ 4 = 6.
Watch for
Equations are not a fact family merely because they share one number. They must express the same whole relationship with inverse operations.
Common mix-up
A fact family does not always have four different written equations. Repeated numbers can make two arrangements identical, as with 3 + 3 = 6.
Exact meaning
A fact family is a set of related number sentences using the same quantities and inverse operations. For a + b = c, it links addition and subtraction facts; for a × b = c with nonzero factors, it links multiplication and division facts.