GMAT
题目
Water flows into an empty swimming pool at a constant rate of 50 liters per minute. If the pool's total capacity is 120 cubic meters, approximately how many hours does it take until the pool is filled to 2/3 of its total capacity? (1 liter = 1,000 cubic centimeters)
解析
工作量的单位是立方米，耗时的单位需要用小时表示。你可以把速率换算成立方米/小时，或者把工作量和时间换算成升和分钟。通常从大单位换算到小单位会更简单。
\( 1\ \text{升} = 1000\ \text{立方厘米} \)
工作量 = \( \frac{2}{3} × 120\ \text{立方米} = 80\ \text{米}×\text{米}×\text{米} \)
= \( 80 × 100\ \text{厘米} × 100\ \text{厘米} × 100\ \text{厘米} \)
= \( 80 × 1000 × 1000\ \text{立方厘米} = 80000\ \text{升} \)
耗时 = \( \frac{80000}{50} = 1600\ \text{分钟} \)
= \( \frac{1600}{60}\ \text{小时} ≈ 26.7 \)
答案：C
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