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Find the Missing Number to Complete the Sum

In this worksheet, students will complete a calculation by adding in the missing numbers. It will strengthen their number skills.

'Find the Missing Number to Complete the Sum' worksheet

Key stage:  KS 2

Curriculum topic:   Verbal Reasoning

Curriculum subtopic:   Complete the Calculation

Difficulty level:  

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:

19 = 7 + __

One of the numbers is missing.

So 19 is the same as 7 add something.

Now we have two options, we can count on from 7 to 19 or take away 7 from 19 to work out the missing number.

Following either of these options, we find that the missing number is 12.

19 = 7 + 12


 

Let’s try another:

17 = 20 - __

In this question, the answer of 17 is the same as 20 take away something.

What do we need to take away from 20 to reach 17?

The missing number is 3.

17 = 20 - 3

 

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!

One of the numbers in the calculation below has been taken away by the cheeky number burglar! Can you work out what it is? 

 

__ - 37 = 99

 

Below is another calculation. Can you work out what number is missing, number detective?

 

__ x 3 = 12

 

maths stuff floating in air

Ready for another exciting question, number detective?

One of the numbers has been removed from the calculation below. Any ideas what that number could be?  

 

__ x 10 = 80

 

numbers in smarties

OK, so you've passed the halfway mark!

Can you work out what number has been missed out in the calculation below?

 

38 + __ = 109

 

thinking

Guess what? Here's another calculation with a missing letter!

Can you work out what that missing letter could be, number detective?

 

__ - 36 = 64

 

little boy thinking

Below is another calculation. Can you work out what number has been removed from it, number detective?                                                                                                                  

 

__ x 4 = 28

 

little girl thinking

Keep going, number detective - you're nearly there.

Can you work out what number is missing from the calculation below?

 

__ + 45 = 118

 

 a hole

Here's another juicy calculation to get your teeth into, number detective!

Can you work out what the missing number is?

 

4 x __ = 44

 

teeth

Only two more questions to go now!

What do you think is the number that has been missed out of the calculation below?

 

133 - __ = 90

 

question mark

You have reached the final question in this activity, number detective? Are you excited?!

What do you think you need to do here? That's right - find the missing number in the calculation below!

 

4 x __ = 16

 

girl winning race

  • Question 1

Welcome to another fun activity, number detective!

One of the numbers in the calculation below has been taken away by the cheeky number burglar! Can you work out what it is? 

 

__ - 37 = 99

 

CORRECT ANSWER
136
EDDIE SAYS
How did you get on? For this question, you need to use the opposite operation to the one they have given. The opposite of subtraction is addition, so you do the calculation 99 + 37. You can work this out as 99 plus 3 tens, then add 7. But, did you spot that the easiest way to do this sum is to add on 100, rather than 99, which gives the answer 137. Then all you have to do is subtract the extra unit that you added in at the beginning to make it 136. Doesn't it look easy when you set it out like this?!
  • Question 2

Below is another calculation. Can you work out what number is missing, number detective?

 

__ x 3 = 12

 

maths stuff floating in air

CORRECT ANSWER
4
EDDIE SAYS
Did you spot that this is testing your knowledge of your three times table? For this question, you need to work out how many threes there are in 12. 12 divided by 3 = 4!
  • Question 3

Ready for another exciting question, number detective?

One of the numbers has been removed from the calculation below. Any ideas what that number could be?  

 

__ x 10 = 80

 

numbers in smarties

CORRECT ANSWER
8
EDDIE SAYS
This one is testing your ten times table! To find the answer, you have to work out how many tens there are in 80. So, that means 80 divided by 10 = 8. Fantastic!
  • Question 4

OK, so you've passed the halfway mark!

Can you work out what number has been missed out in the calculation below?

 

38 + __ = 109

 

thinking

CORRECT ANSWER
71
EDDIE SAYS
You're putting in loads of effort! Did you work this one out alright? Here you do the opposite operation to the one in the calculation, so that's subtraction. 109 - 38 can be worked out as 109 - 30 = 79 (3 backwards jumps of 10) and then 79 - 8 = 71.
  • Question 5

Guess what? Here's another calculation with a missing letter!

Can you work out what that missing letter could be, number detective?

 

__ - 36 = 64

 

little boy thinking

CORRECT ANSWER
100
EDDIE SAYS
You're halfway through this activity! Here you do the opposite operation to the one in the calculation, this is addition. So you work out 64 + 36. This can be worked out as 64 + 30 (3 jumps of 10) + 6. You can also use your knowledge of your number bonds to ten to work this out - if you add the numbers in the tens column together they make 9 (so 90) and if you add the numbers in the units column together they make 10. If you add 90 and 10, you end up with 100! Which method did you use?
  • Question 6

Below is another calculation. Can you work out what number has been removed from it, number detective?                                                                                                                  

 

__ x 4 = 28

 

little girl thinking

CORRECT ANSWER
7
EDDIE SAYS
You're doing great! In this question, you need to work out how many fours are in 28. The sum is: 28 divided by 4 = 7. Is that what you got, number detective? Let's try another one ...
  • Question 7

Keep going, number detective - you're nearly there.

Can you work out what number is missing from the calculation below?

 

__ + 45 = 118

 

 a hole

CORRECT ANSWER
73
EDDIE SAYS
Are you getting the hang of these? This calculation can be worked out by using the opposite operation to the one that has been given. So, the opposite operation to adding is subtracting: 118 - 45 can be worked out as 118 - 40 (4 jumps of 10) = 78. And then, 78 - 5 = 73.
  • Question 8

Here's another juicy calculation to get your teeth into, number detective!

Can you work out what the missing number is?

 

4 x __ = 44

 

teeth

CORRECT ANSWER
11
EDDIE SAYS
Did you find the missing number, Detective? This one is testing your knowledge of your four times table. Here you work out how many fours there are in 44: 44 divided by 4 = 11.
  • Question 9

Only two more questions to go now!

What do you think is the number that has been missed out of the calculation below?

 

133 - __ = 90

 

question mark

CORRECT ANSWER
43
EDDIE SAYS
Did you find the number this time? One method here is to subtract 90 from 133. So, you take 9 backwards jumps of ten to make the number 4. However, did you spot that 90 is 10 less than 100? You could subtract 100 from 133 which is 33. Then all you have to do is add the 10 back on and you have the answer 43! Well done if you spotted that little short-cut!
  • Question 10

You have reached the final question in this activity, number detective? Are you excited?!

What do you think you need to do here? That's right - find the missing number in the calculation below!

 

4 x __ = 16

 

girl winning race

CORRECT ANSWER
4
EDDIE SAYS
How did you do with this last question? To find the answer, you need to work out how many fours there are in 16: 16 divided by 4 = 4. Terrific detective work - hope you've had fun with this activity.
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