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Complete the Sum to Find the Missing Number

In this worksheet, students will complete a calculation by adding in the missing number so that both sides are equal. It will strengthen their number skills.

'Complete the Sum to Find the Missing Number' worksheet

Key stage:  KS 2

Curriculum topic:  Verbal Reasoning

Curriculum subtopic:  Complete the Calculation

Difficulty level:  

down

Worksheet Overview

QUESTION 1 of 10

Calling all number detectives!

 

Look at this symbol:

 

 

We know it is the equals sign but what does it actually mean?

It means the same as and doesn’t just mean the answer.

 

Look at the following calculation:

43 - 7 = 12 x __

Both sides of the calculation are equal. The answer to 43 - 7 must be the same as the answer to 12 multiplied by something (our mystery number).

We need to work out the answer to the calculation on the left to help us work out the missing number on the right.

So 43 - 7 = 36.

We need to make the calculation on the right equal 36. 12 x 3 is 36. Therefore the missing number is 3.

boy smiling

 

Let’s try another to check we understand what is happening:

3 x __ = 5 + 7

Here we must work out the right side of the calculation to help us work out the missing number on the left.

So 5 + 7 = 12.

3 x ? = 12

The missing number is 4 as 3 x 4 = 12.

3 x 4 = 5 + 7

 

Pssstt!! Here’s a handy hint to help you reach superstar status:

Remember that equals means the same as and the answers on either side of the equals sign must be the same.


 

In this activity, you will be completing sums by finding the missing number.

Good luck!

 

 

 

 

 

Welcome to another fun activity, number detective!

Below is a calculation where both sides should be equal.

However, one of the numbers has been taken away by the cheeky number burglar! Can you work out what it is

 

 6 x 6 =  112 - __

 

Are you ready for another one, number detective?

 

Below is a calculation where both sides should be equal. 

Can you work out what number has been missed out?

 

48 ÷ 4 =  241 - __

Below is another calculation where both sides should be equal. 

Can you find the missing number?

 

202 - 93  =  68 +  __

 

girl with magnifying glass

Below is a calculation where both sides should be equal. 

Once again, can you find out what number is missing?

 

18 ÷ 6 = 24 ÷ __ =

 

 

You're halfway through this activity already, number detective!

Below is a calculation where both sides should be equal. 

Can you use your detecting skills to find the missing number? 

 

70 ÷ 5 = 203 - __

 

girl with magnifying glass

Here's another delicious sum to tuck into, number detective!

Below is a calculation where both sides should be equal. 

Can you find the mystery number?

 

 215 - 82 = 20 + __

 

question mark

Below is another calculation where both sides should be equal. 

What is the missing number?

 

99 + 84 = 73 + __

 

 

Keep going, number detective, you're nearly at the end!

Below is a calculation where both sides should be equal. 

Can you work out what number has been missed out?

 

7 x 6 = 201 - __

 

 

You're on to the last two questions - terrific work, number detective!

Below is a calculation where both sides should be equal. 

Guess what you have to do with this one? That's right - can you work out what the missing number is?

 

39 ÷ 3 =  242 - __

 

 

 

You've reached the final question - hurrah!!

Below is a calculation where both sides should be equal. 

What has been missed out, number detective?

 

32 ÷ 2 + =  2 x __

 

boy looking excited

  • Question 1

Welcome to another fun activity, number detective!

Below is a calculation where both sides should be equal.

However, one of the numbers has been taken away by the cheeky number burglar! Can you work out what it is

 

 6 x 6 =  112 - __

 

CORRECT ANSWER
76
EDDIE SAYS
How did you get on with the first question, detective? Remember to break it down into stages. To start, you work out the left-hand side: 6 x 6 = 36. Then, you add the number 36 to the right-hand side: 112 - __ = 36. This can then be worked out by doing 112 - 36, which give us 76. Does that make sense?
  • Question 2

Are you ready for another one, number detective?

 

Below is a calculation where both sides should be equal. 

Can you work out what number has been missed out?

 

48 ÷ 4 =  241 - __

CORRECT ANSWER
229
EDDIE SAYS
Remember to work out the calculation from left to right! First, you work out 48 ÷ 4 = 12. Then, 241 - __ = 12 can be solved by doing 241 - 12. Did you get this one alright? The answer is 229.
  • Question 3

Below is another calculation where both sides should be equal. 

Can you find the missing number?

 

202 - 93  =  68 +  __

 

girl with magnifying glass

CORRECT ANSWER
41
EDDIE SAYS
Did you work this one out? First, you have to do 202 - 93 = 109. Then, 68 + __ = 109 can be worked out by doing 109 - 68. It's easier once you break it down isn't it?!
  • Question 4

Below is a calculation where both sides should be equal. 

Once again, can you find out what number is missing?

 

18 ÷ 6 = 24 ÷ __ =

 

 

CORRECT ANSWER
8
EDDIE SAYS
This one is really testing your times tables knowledge! How did you do? First, you need to do 18 ÷ 6 = 3. Then, solve 24 ÷ __ = 3 by counting how many threes there are in 24. Great detective work!
  • Question 5

You're halfway through this activity already, number detective!

Below is a calculation where both sides should be equal. 

Can you use your detecting skills to find the missing number? 

 

70 ÷ 5 = 203 - __

 

girl with magnifying glass

CORRECT ANSWER
189
EDDIE SAYS
How did you do? First of all, you have to do 70 ÷ 5 = 14. Then, 203 - __ = 14 can be solved by doing 203 - 14, which makes 189. Oh, what fun. You're halfway done!
  • Question 6

Here's another delicious sum to tuck into, number detective!

Below is a calculation where both sides should be equal. 

Can you find the mystery number?

 

 215 - 82 = 20 + __

 

question mark

CORRECT ANSWER
113
EDDIE SAYS
You're hunting down a lot of numbers, detective! How did you get on with this rather trickier one? For this question, you do 215 - 82 = 133. Then, 20 + __ = 133 can be solved by doing 133 - 20, which is 113. Easy really when you break it down!!
  • Question 7

Below is another calculation where both sides should be equal. 

What is the missing number?

 

99 + 84 = 73 + __

 

 

CORRECT ANSWER
110
EDDIE SAYS
Let's work it through. First, you need to do 99 + 84 = 183. Then, 73 + __ = 183 can be solved by doing 183 - 73, which gives us 110. Fantastic!
  • Question 8

Keep going, number detective, you're nearly at the end!

Below is a calculation where both sides should be equal. 

Can you work out what number has been missed out?

 

7 x 6 = 201 - __

 

 

CORRECT ANSWER
159
EDDIE SAYS
Let's go through it slowly. The first step is to do 7 x 6 = 42. Then, 201 - __ = 42 can be solved by doing 201 - 42, which is 159.
  • Question 9

You're on to the last two questions - terrific work, number detective!

Below is a calculation where both sides should be equal. 

Guess what you have to do with this one? That's right - can you work out what the missing number is?

 

39 ÷ 3 =  242 - __

 

 

 

CORRECT ANSWER
229
EDDIE SAYS
Let's look at it a bit at a time. First, do 39 ÷ 3 = 13. Then, 242 - __ = 13 can be solved by doing 242 - 13, which is 229. Now let's take a peek at the last question in this activity!
  • Question 10

You've reached the final question - hurrah!!

Below is a calculation where both sides should be equal. 

What has been missed out, number detective?

 

32 ÷ 2 + =  2 x __

 

boy looking excited

CORRECT ANSWER
8
EDDIE SAYS
How did you do with this last question? First of all, work out 32 ÷ 2 = 16. Then, 2 x __ = 16 can be worked out by finding how many twos there are in sixteen (16 ÷ 2). This activity is now complete, the missing numbers have been collected and inspected. You are a great number detective!
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