Profit, loss and discount
Objective. Solve contextual percentage problems and justify decisions.
- 1. Learn
- 2. Worked example
- 3. Practice
- 4. Feedback
- 5. Continue
Learn: the key idea
Profit, loss and discount problems apply percentage calculations to buying and selling contexts, where you compare a cost price with a selling price. Profit occurs when the selling price is higher than the cost price, and the percentage profit is the profit divided by the cost price, multiplied by 100. A discount reduces a marked price by a percentage before the item is sold. To decide whether a deal is worthwhile, calculate the actual amounts involved and compare them directly rather than just comparing percentages, since the same percentage can mean different amounts on different prices.
Worked example
A shop buys a lamp for £40 and sells it for £52. Calculate the percentage profit made on the lamp.
- 1Find the profit: £52 − £40 = £12
- 2Write profit over cost price: 12/40
- 3Convert to a percentage: (12 ÷ 40) × 100
- 4Calculate the result: 30%
Answer: 30%
Concept mastery
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Practice
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Start practisingCommon mistake. Pupils often calculate percentage profit using the selling price as the denominator instead of the cost price, so a £20 profit on a £80 cost item is wrongly divided by £100 instead of £80, giving 20% instead of the correct 25%.
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