This activity is about calculating a percentage decrease.

**We are using a calculator for this activity!**

We can see percentage decreases everywhere.

A common place to see them is in shops when they have a sale!

We can calculate simple percentage decreases easily without a calculator.

For example, a pair of trainers were £60 but there was 20% off in the sale.

We can work out 20% of 60 and subtract the answer from 60.

So, 10% of 60 = £6

20% = 2 x 10% = 2 x £6 = £12

Sale price = £60 - £12 = £48

When they get a little more tricky, like a 47% decrease, it is easier and quicker to use a **multiplier** and a calculator!

**Recap - the multiplier is basically, the decimal!**

__Example__

Decrease 35 ml by 15%.

**Answer**

To find 15% it is 15/100 = 15 ÷ 100 = 0.15 as a decimal.

If we decrease by 15% then we want the other 85%.

**Decrease** means we are **taking away 15%** so we **want 85%. **

So, we could do the whole thing in one move:

**A decrease of 15% means 100% - 15% = 85% = 0.85**

0.85 x 35 ml to get the 15% decrease.

**35 ml x 0.85 = 29.75 ml**

It is a bit tricky, but it will become easier with practice.

Let's try some questions.