Percentage Increase and Decrease

In a Nutshell

To increase by a percentage, add it on. To decrease, take it off. Or use a multiplier for speed.

A percentage increase means the amount gets bigger. A percentage decrease means it gets smaller. You already know how to find a percentage of an amount. Now you just add or subtract the result.

There are two approaches:

Method 1 (two steps): Find the percentage, then add or subtract it.

Method 2 (multiplier): Use a single multiplication. An increase of $20\%$ means you end up with $120\%$ of the original, so multiply by $1.2$ . A decrease of $20\%$ means you keep $80\%$ , so multiply by $0.8$ .

\text{New amount} = \text{Original} \times \text{multiplier}

Total amount Percentage

Set the total amount and a percentage. The shaded bar shows the percentage portion. For an increase, you would add this to the original. For a decrease, you would subtract it.

Watch it work

Question 1: Increase $450$ by $12\%$ .

Question 2: Decrease $\pounds 80$ by $30\%$ using a multiplier.

Have a go

Q1. Increase $200$ by $15\%$ .

Q2. Decrease $500$ by $40\%$ .

Q3. A shop increases the price of a £45 shirt by $10\%$ . What is the new price?

Q4. A car worth £12,000 loses $25\%$ of its value in the first year. What is it worth after one year?

Q5. Use a multiplier to increase $640$ by $5\%$ .