Problem 1 · 2001 AMC 8
Easy
Ratios, Rates & Proportions
unit-rate
Casey's shop class is making a golf trophy. He has to paint 300 dimples on a golf ball. If it takes him 2 seconds to paint one dimple, how many minutes will he need to do his job?
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Answer: D — 10 minutes.
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Hint 1 of 2
The question asks for minutes, but everything is given in seconds — that's two jobs: find the time, then switch the unit.
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Hint 2 of 2
Total seconds = (seconds per dimple) × (dimples); minutes = seconds ÷ 60.
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Approach: total time, then change units
- Painting all 300 dimples takes 2 × 300 = 600 seconds.
- Now switch units: 600 seconds ÷ 60 = 10 minutes.
- Watch the units the question wants. Here it asks for minutes, so an answer of 600 would be a trap — you'll see this trick again whenever a problem feeds you one unit and asks for another.
Another way — convert the rate first:
- 2 seconds per dimple means he paints 30 dimples per minute (60 ÷ 2).
- 300 dimples ÷ 30 per minute = 10 minutes — no big numbers needed.
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