AQA · Mathematics · 8300
GCSE Maths: Percentages: increasing\decreasing
Ratio & Proportion · AQA GCSE Maths (8300). Cards are generated from the Corbettmaths practice questions and answers for Percentages: increasing\decreasing (Corbettmaths Video 238), and every card links back to the exact page it came from. Practice tests generate fresh variations of these questions, so the numbers change every attempt. Source material © Corbettmaths — used with attribution.
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To increase £2400 by 9%, what calculation method can you use?
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Multiply £2400 by 1.09 (or calculate 9% and add it to the original amount).
To decrease a value by 24%, what multiplier should you use?
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0.76 (which is 1 - 0.24)
A ball bounces to 80% of its previous height each time. If dropped from 3m, what height does it reach after the second bounce?
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1.92m. After the first bounce it rises to 3 × 0.8 = 2.4m. After the second bounce it rises to 2.4 × 0.8 = 1.92m.
A house value decreases by 10% then increases by 10%. Is the final value more, less, or the same as the original?
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Less. The 10% decrease is calculated on the original amount, but the 10% increase is on the smaller reduced amount, so the increase is smaller than the decrease.
A quantity is decreased by 40%. What multiplier represents this change?
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0.6 (or 60%). A 40% decrease leaves 100% - 40% = 60% of the original, which is 0.6 as a decimal.
A quantity is increased by 10%. What multiplier represents this change?
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1.1 (or 110%). A 10% increase gives 100% + 10% = 110% of the original, which is 1.1 as a decimal.
A house worth £340,000 increases by 15% then by 9%. What is the increase in value from the original?
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£81,690. After 15%: £340,000 × 1.15 = £391,000. After 9%: £391,000 × 1.09 = £426,690. Increase: £426,690 - £340,000 = £81,690.
A rectangle with length 1.2m and width 0.5m has both dimensions increased by 35%. By what percentage does the area increase?
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82.25%. Original area: 0.6m². New dimensions: 1.62m × 0.675m = 1.0935m². Percentage increase: (1.0935 - 0.6) / 0.6 × 100 = 82.25%.
If both dimensions of a rectangle are increased by x%, does the area also increase by x%?
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No. The area increases by more than x%. When both dimensions are multiplied by (1 + x/100), the area is multiplied by (1 + x/100)², which is greater than (1 + x/100).
To find the result of increasing a value by 15%, multiply the original by ?
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1.15
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