Practise Using Addition and Subtraction Family Groups

This activity is all about families.

 

 

No, not that sort of family -  maths families!

 

Addition and subtraction family facts normally come in fours. 

There are two addition facts and two subtraction facts.

 

If we know just one of them, we can always work out the other three.

 

If we know the addition fact that

3 + 5 = 8

we can say that the other addition fact in this family is

5 + 3 = 8

 

The subtraction facts in this family will be

8 - 5 = 3

and

8 - 3 = 5

 

Got that?

 

 

Example

What are the three related family facts for...?

15 + 18 = 33

 

Answer

For the other addition fact, just reverse the first two numbers.

The other addition fact in this family is

18 + 15 = 33

 

For the subtraction fact, we start with the biggest number.

The subtraction facts in this family will be

33 - 15 = 18

and

33 - 18 = 15

 

Easy stuff, yes? Let's have a go at some questions now.