Percentage discounts & sale price
Theory
A discount is a percentage taken off a price. Find the discount, then subtract it: sale price \(=\) original \(-\) discount. The percentage left is \(100\%\) minus the discount.
A discount is an amount taken off a price. It is worked out as a percentage of the original price.
The friendly discounts are quick: \(10\%\) is \(\div 10\), \(25\%\) is \(\div 4\), and \(50\%\) is \(\div 2\).
The sale price is what is left: sale price \(=\) original price \(-\) discount.
The percentage left is \(100\%\) minus the discount, so \(25\%\) off leaves \(75\%\) of the price.
Each friendly discount has a fast division and a percentage that stays behind.
| Discount | Find it by | Percentage left |
|---|---|---|
| 10% off | divide by \(10\) | 90% |
| 25% off | divide by \(4\) | 75% |
| 50% off | divide by \(2\) | 50% |
How to find a sale price
- Find the discount. Work out the percentage of the original price.
- Subtract. Take the discount off the original price to get the sale price.
- Check what is left. The percentage left is \(100\%\) minus the discount.
Discount $9, sale price $81.
| \(90 \div 10\) | \(=\) | \(9\) |
| \(90 - 9\) | \(=\) | \(81\) |
The sale price is $36.
| \(48 \div 4\) | \(=\) | \(12\) |
| \(48 - 12\) | \(=\) | \(36\) |
Half off leaves half, so the sale price is $60.
| \(120 \div 2\) | \(=\) | \(60\) |
75% is left; the sale price is $150.
| \(100\% - 25\%\) | \(=\) | \(75\%\) |
| \(200 \div 4\) | \(=\) | \(50\) |
| \(200 - 50\) | \(=\) | \(150\) |
Common pitfalls
Frequently asked questions
How do you work out a sale price?
Find the discount, then subtract it from the original price. For a $90 jacket with \(10\%\) off: \(90 \div 10 = 9\), then \(90 - 9 = 81\).
How do you find the discount?
Take the percentage of the original price. \(10\%\) is \(\div 10\), \(25\%\) is \(\div 4\), \(50\%\) is \(\div 2\).
What percentage is left after a 25% discount?
\(75\%\). The whole price is \(100\%\), so \(100\% - 25\% = 75\%\) is left.
Is 10% off the same as dividing by 10?
The discount is \(\div 10\), but the sale price is not. After finding the discount you must subtract it, so \(80 \div 10 = 8\) off leaves \(72\).
Which saves more, 25% off or 50% off?
On the same price, \(50\%\) off saves more. On $100 that is $50 saved, compared with $25 for \(25\%\) off.