Problem 2 · 2005 AMC 8
Easy
Fractions, Decimals & Percents
percent-of-amount
Karl bought five folders from Pay-A-Lot at a cost of $2.50 each. Pay-A-Lot had a 20%-off sale the following day. How much could Karl have saved on the purchase by waiting a day?
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Answer: C — $2.50.
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Hint 1 of 2
The savings is just the discount — 20% of what he actually spent. You only need that piece, not the new price.
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Hint 2 of 2
20% means 'one fifth.' Taking a fraction is often faster than multiplying by a decimal.
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Approach: savings = the discount itself
- He spent 5 · $2.50 = $12.50 on the folders.
- Saving 20% means saving one fifth: $12.50 ÷ 5 = $2.50.
- Shortcut worth keeping: 'percent off' is a fraction in disguise — 20% = 1/5, 25% = 1/4, 50% = 1/2. Dividing by the fraction's denominator beats reaching for the calculator.
Another way — discount per folder, then scale:
- Each folder's discount is 20% of $2.50 = $0.50.
- Five folders: 5 · $0.50 = $2.50. Same answer, and you never need the $12.50 total at all.
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