# Find the Correct Number Operation

In this worksheet, students will learn about addition, multiplication, division and subtraction facts and use this to work out a missing number.

Key stage:  KS 2

Curriculum topic:   Verbal Reasoning

Curriculum subtopic:   Number Logic

Difficulty level:

### QUESTION 1 of 10

Hi number detective! We’ve got another challenge that we need your help with. Are you ready?

6 (18) 3

How could the two outside numbers (6 and 3), make the inside number (18)?

We can use any of the four main number operations to make our number.

These are addition, subtraction, multiplication and division.

If we return to our problem, we can see that 6 &times; 3 = 18.

So the rule here is that the outside numbers multiply together to make the inside number.

For this question, we need to work out the rule for the first set of numbers and then use that rule to work out the missing number in the next set.

Let’s look at a problem with two sets of numbers now:

3 (7) 4, 6 ( __ ) 10

First, let’s work out how the numbers 3 and 4 make 7.

They add together to make 7.

We need to use the rule of adding the outside numbers for 6 and 10 to work out the missing number.

6 and 10 add together to make 16 so the missing number is 16.

Let’s try another one:

12 (7) 5, 20 ( __ ) 4

First, we need to work out how the numbers 12 and 5 can make 7.

12 - 5 = 7. This means we are taking away the number on the right from the number on the left.

We need to apply this rule to the second pair of numbers giving us 20 - 4 which is 16.

Does that make sense?

It’s now your turn to put your skills to the test and become a number detective, hunting down those missing numbers!

Hey number detective, welcome to an exciting number activity!

Look at the number problem below:

5 ? 3 = 15

Select the number operation below that would replace the question mark.

+ - x ÷

Look at the number problem below:

7  ?  3 = 10

Click on the number operation symbol that should replace the question mark.

+ - x ÷

Which number operation symbol should replace the question mark below?

11 ? 3 = 8

+ - x ÷

How are you getting on with these so far, number detective?

Which number operation would complete the number sentence below?

10 ? 2 = 5

+ - x ÷

Hey number detective, you're halfway there already!

Look at the number problem below:

5 (20) 4

How could the two outside numbers (5 and 4) make the inside number (20)?

Subtraction

Multiplication

Division

Here's another puzzle for you detective:

6 (10) 4

Which number operation is used to make the inside number (10) with the two outside numbers (6 and 4)?

Subtraction

Multiplication

Division

You're doing so well, number detective.

Which number operation is used to make the middle number (3) using the two outside numbers (7 and 4)?

7 (3) 4

Subtraction

Multiplication

Division

Which number operation uses the outside two numbers (50 and 10) to make the inside number (5)?

50 (5) 10

Subtraction

Multiplication

Division

Right, number detective... I need you to put all your skills to the test now.

Match the number sentences below to their missing number operations.

## Column B

5 ? 7 = 35
-
12 ? 5 = 17
x
10 ? 7 = 3
+
12 ? 2 = 6
÷

It's time for your final mission, number detective!

Match each number problem to their number operation rule.

## Column B

3 (10) 7
Number on the left subtracts the number on the rig...
2 (16) 8
Number on the left is divided by the number on the...
20 (2) 10
Outside numbers add to make the inside number
17 (10) 7
Outside numbers multiply to make the inside number
• Question 1

Hey number detective, welcome to an exciting number activity!

Look at the number problem below:

5 ? 3 = 15

Select the number operation below that would replace the question mark.

+ - x ÷
EDDIE SAYS
I hope you have your maths hat on, detective! We need to work out how we can make the number 15 by using 5 and 3. 5 x 3 = 15 so the correct answer here is multiplication (x). Top tip: work your way through the four main number operations until you get the correct answer. If you got this wrong, don't panic - all you need to do is to keep on practising which we will do together.
• Question 2

Look at the number problem below:

7  ?  3 = 10

Click on the number operation symbol that should replace the question mark.

+ - x ÷
EDDIE SAYS
How do the numbers 7 and 3 make 10? We add them. Did you try the other operations just to check that they were incorrect? If not, then let's do that together now. 7 - 3 = 4 - not the right answer 7 x 3 = 21 - not the right answer 7 ÷ 3 - will not give you a whole number, so this isn't right! So, it has to be 7 + 3 = 10 7 + 3 = 10 so the missing symbol is +. Do you know all of your number bonds to 10? If not you need to learn them, detective!
• Question 3

Which number operation symbol should replace the question mark below?

11 ? 3 = 8

+ - x ÷
EDDIE SAYS
The missing operation here was take away! 11 - 3 = 8 Did you try out all four number operations until you found the one that worked? 11 + 3 = 14 - not the right answer 11 - 3 = 8 - yes, that's the one! 11 x 3 = 33 - not the right answer 11 ÷ 3 - does not leave us with a whole number. So, the only one that works is 11 - 4 which equals 8. Did you get this one, number detective?
• Question 4

How are you getting on with these so far, number detective?

Which number operation would complete the number sentence below?

10 ? 2 = 5

+ - x ÷
EDDIE SAYS
How do the numbers 10 and 2 make 5? 10 ÷ 2 = 5 so the missing symbol is ÷. 10 ÷ 2 means how many 2s go into 10. If you count up in 2s on your fingers, you'll see that 5 of them make 10. None of the other operations would work: 10 + 2 = 12 - not the right answer 10 - 2 = 8 - not the right answer 10 x 2 = 20 - not the right answer None of these sums gives us the correct answer, so we've found that only division can be right! Great detective work- keep up the excellent mental maths!
• Question 5

Hey number detective, you're halfway there already!

Look at the number problem below:

5 (20) 4

How could the two outside numbers (5 and 4) make the inside number (20)?

Multiplication
EDDIE SAYS
How did you get on with this one? We need to work out how the numbers 5 and 4 make 20. If you try out all four number operations, you'll see that 5 x 4 = 20. Use your knowledge of the 5 times table: 5, 10, 15, 20. I'm counting on you to check all of the number operations carefully to see which one solves the puzzle. Let's test them out so that you get the idea: 5 + 4 = 9 - not the right answer 5 - 4 = 1 - not the right answer 5 x 4 = 20 - yes, that's the one! 5 ÷ 4 - doesn't give us a whole number so isn't right! Let's try another one together.
• Question 6

Here's another puzzle for you detective:

6 (10) 4

Which number operation is used to make the inside number (10) with the two outside numbers (6 and 4)?

EDDIE SAYS
How can we make 10 with 6 and 4? 6 + 4 = 10 so this makes addition the correct answer. Did you know 6 and 4 were number bonds to 10 just by looking at them? It's important that we know our number bonds off by heart. Did you try out the other operations just to check that they were not correct? 6 - 4 = 2 - not the right answer 6 x 4 = 24 - not the right answer 6 ÷ 4 - doesn't give us a whole number so can't be right. It's important to check the other signs before entering your final answer.
• Question 7

You're doing so well, number detective.

Which number operation is used to make the middle number (3) using the two outside numbers (7 and 4)?

7 (3) 4

Subtraction
EDDIE SAYS
Are you getting the hang of these yet? Did you manage to work out how to make 3 by using 7 and 4? 7 - 4 = 3 Therefore, we know that this puzzle requires subtraction. Try out all of the number operations until you find one which gives you the correct answer. You can use your fingers to count carefully if you need to. Only three more questions to go, quickly onto the next one!
• Question 8

Which number operation uses the outside two numbers (50 and 10) to make the inside number (5)?

50 (5) 10

Division
EDDIE SAYS
How did you find this? You needed to work out how we can make an answer of 5 by using the numbers 50 and 10. Addition wouldn't work as 50 + 10 = 60 Subtraction wouldn't work as 50 - 10 = 40 Multiplication wouldn't work as 50 x 10 = 500 Let's try division: 50 ÷ 10 = 5 Puzzle solved! The correct answer is division. Keep your eyes peeled for more number puzzles, detective!
• Question 9

Right, number detective... I need you to put all your skills to the test now.

Match the number sentences below to their missing number operations.

## Column B

5 ? 7 = 35
x
12 ? 5 = 17
+
10 ? 7 = 3
-
12 ? 2 = 6
÷
EDDIE SAYS
How many matches did you find detective? 5 x 7 = 35 12 + 5 = 17 10 - 7 = 3 12 ÷ 2 = 6 We had one for each number operation here! I know it can take a while to check each number operation for each question, but it's totally worth it as it helps you get the right answer! Let's move on to the final question in this activity.
• Question 10

It's time for your final mission, number detective!

Match each number problem to their number operation rule.

## Column B

3 (10) 7
Outside numbers add to make the i...
2 (16) 8
Outside numbers multiply to make ...
20 (2) 10
Number on the left is divided by ...
17 (10) 7
Number on the left subtracts the ...
EDDIE SAYS
There were lots of puzzles to solve here! Did you find some of the matches? 3 (10) 7 --> 3 + 7 = 10 2 (16) 8 --> 2 x 8 = 16 20 (2) 10 --> 20 ÷ 10 = 2 17 (10) 7 --> 17 - 7 = 10 You are now a pro at all four number operations. Great work, detective! You should now feel confident when asked to apply or inverse basic number operations.
---- OR ----