A ratio is a method in maths that is used to compare two (or more) quantities.

So, for example, if I had 3 red balls and 9 blue balls, the ratio of red to blue balls would be 3:9

One thing that is vital in ratio is remembering that the order is important.

**Cancelling a ratio**

When you are trying to cancel a ratio, the rules are the same as if you were trying to cancel a fraction. You need to find the Highest Common Factor (HCF) and then divide by that.

**Example 1: Cancel 9:3 to its simplest form.**

The Highest Common Factor of 9 and 3 is 3, so we divide both sides by 3

3:1

**Example 2: Simplify 25:85 as far as possible.**

The HCG of 25 and 85 is 5, so we divide both by 5.

5:17

**Example 3: Write £2 to 30p as a ratio in its simplest form. **

The key thing to notice here is that the units aren't the same so we have to change this.

Remember as well that the order for the ratio must be the same as in the question

£2 : 30 p

200 p : 30 p

Now we can cancel down, we can also get rid of the units now they are the same. The HCF here is 10, so we divide by 10.

20: 3