Fact Families

Concept

In math, a fact family can be defined as a group of math facts or created using the same set of numbers. The fact family shows the relationships between the three numbers involved.
In an addition and subtraction fact family, there are four addition and subtraction sentences created using three numbers. Similarly, in a multiplication and division fact family, there are multiplication and division sentences created using three numbers.

We can use fact families to reinforce or learn the connection between addition and subtraction, and to help learners memorize the basic addition & subtraction facts.

There are two types of fact families: an addition/subtraction family and a multiplication/division family.

Rules

– All 3 numbers in a fact family are related.
– They are the only numbers that can be used.
– There are 2 addition facts and 2 subtraction facts in each fact family.
– The addition facts end with the greatest number.
– The subtraction facts begin with the greatest number.
– The greatest number is always written at the top corner of the triangle.

Example

Complete the fact triangle using fact family.

Solution

We know from the rules that the greatest number is always written at the top corner of the triangle.
Therefore the greatest number here is 19.

We have to find the number that adds to 9 and makes 19. Let’s list all the facts using the given numbers.
1. 19 – 9 = 10
2. 9 + 10 = 19
3. 19 – 10 = 9
4. 10 + 9 = 19

We can see that the missing number that completes the fact triangle is 10.