Problem 3 · 2020 AMC 8
Easy
Arithmetic & Operations
unit-rate
Carrie has a rectangular garden that measures 6 feet by 8 feet. She plants the entire garden with strawberry plants. Carrie is able to plant 4 strawberry plants per square foot, and she harvests an average of 10 strawberries per plant. How many strawberries can she expect to harvest?
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Answer: D — 1920 strawberries.
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Hint 1
Follow the units like a relay: square feet → plants → strawberries. Each “per” is just a multiply, and the units hand off cleanly down the chain.
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Approach: chain the per-unit rates
- Area: 6 ft × 8 ft = 48 sq ft.
- Plants: 48 sq ft × 4 plants/sq ft = 192 plants.
- Strawberries: 192 plants × 10 berries/plant = 1920.
- You'll see this again as: chained “per” rates just multiply, and the units cancel like a relay baton (sq ft → plants → berries). Tracking the words stops you from dividing when you should multiply.
Another way — regroup the easy factors first:
- 4 plants/sq ft × 10 berries/plant = 40 berries per square foot.
- 48 sq ft × 40 = 1920. Multiplying the small numbers together first keeps the arithmetic light.
Mark:
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