  # Using Adding and Subtracting Family Groups (1)

In this worksheet, students must know that addition and subtraction are inverses and use this fact to find the missing number. Key stage:  KS 1

Curriculum topic:   Number: Addition and Subtraction

Curriculum subtopic:   Understand Relationship Between Addition and Subtraction

Difficulty level:   #### Worksheet Overview

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

23 + 35 = 58

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

35 + 23 = 58

The subtraction facts in this family will be

58 - 35 = 23

and

58 - 23 = 35

Example

15 + 18 = 33

to work out the missing number below:

33 - = 15

15 + 18 = 33

So 33 - 18 = 15 and 33 - 15 = 18

The missing number is 18.

33 - 18  = 15

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