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

In these questions, we will have to use a third top secret number as well as our main four operations: **addition, subtraction, multiplication **and** division.**

How do the numbers on the outside of the brackets create the numbers on the inside of the brackets?

**5 (33) 7 6 (22) 4**

The first thing to do is find a way to make **33** using** 5** and **7 **together with **an invisible secret number**.

We know that 5 x 7 = 35 which is close to our target of 33.

We can guess that the **secret number is 2** and that we need to **take this away** from our total to reach **33**.

So our rule could be: multiply the two outside numbers together and then take away 2.

Let’s see if this rule works for our next set of numbers!

If we apply it, we get **6 x 4 = 24**. Then if we take away the **secret 2**, we get 22.

This is the number we are aiming for so we’ve cracked the code! Well done!

For the next question we need to crack the code and then use the rule to work out a missing number:

**3 (11) 5 4 (16) 9 2 (_) 7**

First, we need to find a way to make **11 **using **3** and **5** together with **an invisible secret number**.

We could try **3 x 5 = 15** and then take away the secret number of **4** to get **11**.

So our rule could be: multiply the two outside numbers and then take away 4.

Let’s see if this rule works for the next set of numbers: **4 x 9 = 36 **and **36 - 4 = 32**.

Oh dear! We didn’t find the right rule this time which means we need to look for another.

We could try **3 + 5 = 8** and then add a secret number of **3**.

So our rule could be: add the two outside numbers and then add an extra 3.

Let’s try that for the next set of numbers:** 4 + 9 = 13** and then add the extra **3** is **16**.

Jackpot! We’ve found the right rule!

Now let’s use this rule to work out the missing number in the final set of numbers.

**2 + 7 = 9 **and then add the extra **3** gives us **12**.

So the correct answer is **12**.

Pssstt!! Here's a handy hint to help you reach superstar status: Look out for the secret number and don't worry if the first rule you find doesn't work, just stay calm and try another one! |

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