In this activity, we will learn to identify the missing numbers in a given sequence.

**Look at this sequence.**

15 | 18 | 21 | 24 | 27 | 30 | 33 |

It goes up in steps of 3.

So, the rule for this sequence is 'add 3'.

Let's look at another sequence. This time some numbers are missing.

A | 22 | 29 | 36 | 43 | B | C |

To find the missing numbers, we first work out the differences between the existing numbers in the sequence.

The difference between 22 and 29 is 7.

29 - 22 = 7

The difference between 36 and 43 is also 7.

43 - 36 = 7

So, we know the numbers in this sequence go **up in 7s**.

We can find the first missing number by **counting back **7 from 22.

22 - 7 = **15**

Then, we can find the second and third missing numbers by **counting on** in steps of 7.

43 + 7 = **50**

50 + 7 = **57**

The missing numbers are **15, 50 and 57.**

15 | 22 | 29 | 36 | 43 | 50 | 57 |

Now let's try an example.

**Example:**

Find the missing numbers in the sequence.

A | 17 | 22 | 27 | 32 | B | C |

**Answer:**

22 - 7 = 5

27 - 22 = 5

32 - 27 = 5

This sequence is **counting in 5s.**

So the first missing number is 17 - 5 = **12.**

The last two numbers are **37 and 42.**

12 | 17 | 22 | 27 | 32 | 37 | 42 |

Now it's your turn to work out some missing numbers in sequences.