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Deduce the Missing Number in Subtractions Mentally

In this worksheet, students will be asked to use efficient mental methods to subtract mentally. They will use the inverse operation to calculate a missing number.

'Deduce the Missing Number in Subtractions Mentally' worksheet

Key stage:  KS 2

Curriculum topic:   Number: Addition and Subtraction

Curriculum subtopic:   Add/Subtract Mentally

Difficulty level:  

Worksheet Overview

In this activity, you will be asked to find the missing number in a subtraction question.

The key to this activity is calculating every answer mentally (in your head) without using pen and paper.

 

Example 1

In your head, find the missing number

 

    - 14 = 24

 

Answer

Use the inverse operation (addition) in order to find the answer

14 + 24 = 38

 

Check

38 - 14 = 24

 

 

Example 2

    - 0.6 = 2

 

Answer 

Use the inverse operation in order to find the answer:

2 + 0.6 = 2.6

 

Check

2.6 - 0.6 = 2

 

 

Example 3

34 -  = 11

 

Answer 

Use the numbers you have been given to complete a subtraction sum in order to find the missing number

34 - 11 = 23

 

Check

34 - 23 = 11

 

This method will make more sense when you attempt to answer some questions.

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