Percentage change
Objective. Solve simple percentage increase, decrease and discount problems.
- 1. Learn
- 2. Worked example
- 3. Practice
- 4. Feedback
- 5. Continue
Learn: the key idea
A percentage change describes how much a quantity has increased or decreased relative to its original value. To increase an amount by a percentage, add that percentage of the amount to the original; to decrease, subtract it instead. For example, increasing £80 by 20% means adding 20% of 80, which is 16, giving £96. A quicker method multiplies by a single decimal: increasing by 20% multiplies by 1.2, while decreasing by 20% multiplies by 0.8. Discounts in shops are decreases, so a 25% discount on £40 removes £10, leaving £30 to pay.
Worked example
A jacket costing £60 is reduced in a sale by 15%. Find the percentage change applied and the new price.
- 1Find 10% of £60: £6.
- 2Find 5% of £60 by halving: £3.
- 3Add to make 15%: 6+3=£9.
- 4Subtract the discount from the original price: 60−9=£51.
Answer: New price £51 after a 15% decrease
Concept mastery
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Practice
Practice happens on its own screen, one question at a time. Answers stay hidden until you submit yours, and you can stop and pick up at the same question later.
Start practisingCommon mistake. Pupils sometimes calculate the percentage of the amount correctly but forget to add or subtract it from the original, leaving just the percentage value as their final answer. Always complete the increase or decrease step.
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