**Common Multiples of Two-Digit Numbers** *KS2 Revision*

## What you need to know

**Things to remember:**

- Common multiples are multiples that are the same for two numbers.
- Multiplying two numbers together gives a common multiple of these two numbers.
- There is an infinite number of multiples, they go on forever!

So, what are multiples of a number? They’re just the times table!

7 times table:

**7 14 21 28 35 42 49 56 63 70**

Multiples of 7:

**7 14 21 28 35 42 49 56 63 70**

We can see that these are the same thing!

Now that we know how to find multiples, how can we find **common multiples** of two numbers? Well, all we do is list the multiples of the two numbers and see if there are any that appear in both!

What are some common multiples of 8 and 18?

We will do this in two steps:

**Step 1: **Write out some of the multiples of both numbers.

Multiples of 8

**8 16 24 32 40 48 56 64 72 80**

Multiples of 18

**18 36 54 72 90 108 126 144 162 180**

If we look at these two lists of multiples, we can see that 72 appears in both lists. So, this means that 72 is a common multiple of 8 and 18.

If we were to keep writing out the multiples of 8, we’d eventually get to the number 144. Notice how 144 is a multiple of 18 as well. More importantly:

8\times18=144

So, multiplying two numbers together will always make a common multiple!

Find a common multiple 18 and 15:

18\times=270

270 is a common multiple of 18 and 15.

** **

Find a common multiple of 4 and 6:

4\times6=24

24 is a common multiple of 4 and 6.

## Example Questions

**Question 1: **What are the first 4 common multiples of 4 and 6?

Multiples of 4

**4 8 12 16 20 24 28 32 36 40 44 48**

Multiples of 6

**6 12 18 24 30 36 42 48 54 60**

The first 4 common multiples of 4 and 6 are: 12, 24, 36, and 48.

**Question 2:** Find a common multiple of 27 and 25.

27\times25=675

675 is a common multiple of 25 and 27.