Percentages
Ten quantitative aptitude questions, each marked as you answer.
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The population of a town is 51,000. It grows by 10% every year. What will it be after 2 years?
Answer and working
Answer A
51,000 × (1 + 10/100)² = 51,000 × 1.21 = 61,710. Growing 10% on 51,000 twice, not 20% once.
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A number is first increased by 25% and then decreased by 25%. What is the net change?
Answer and working
Answer C
Net effect = 25 − 25 − (25 × 25)/100 = −6.25%, so 6.25% decrease.
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The population of a town is 21,200. It grows by 5% every year. What will it be after 2 years?
Answer and working
Answer C
21,200 × (1 + 5/100)² = 21,200 × 1.1 = 23,373. Growing 5% on 21,200 twice, not 10% once.
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The population of a town is 35,200. It grows by 5% every year. What will it be after 2 years?
Answer and working
Answer D
35,200 × (1 + 5/100)² = 35,200 × 1.1 = 38,808. Growing 5% on 35,200 twice, not 10% once.
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What is 25% of 760?
Answer and working
Answer B
25% of 760 = 760 × 25/100 = 190.
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A number is first increased by 10% and then decreased by 30%. What is the net change?
Answer and working
Answer D
Net effect = 10 − 30 − (10 × 30)/100 = −23%, so 23% decrease.
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A number is first increased by 20% and then decreased by 25%. What is the net change?
Answer and working
Answer B
Net effect = 20 − 25 − (20 × 25)/100 = −10%, so 10% decrease.
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A number is first increased by 50% and then decreased by 30%. What is the net change?
Answer and working
Answer C
Net effect = 50 − 30 − (50 × 30)/100 = 5%, so 5% increase.
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16 is what percent of 400?
Answer and working
Answer A
16 ÷ 400 × 100 = 4%.
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A number is first increased by 30% and then decreased by 30%. What is the net change?
Answer and working
Answer B
Net effect = 30 − 30 − (30 × 30)/100 = −9%, so 9% decrease.
More quantitative aptitude: Profit, loss and discount, Simple interest, Compound interest, Ratio and proportion, Averages, Problems on ages.