Pipe A fills a tank in 30 hours and pipe B fills it in 20 hours. Working together, how many hours do they need?
Answer and explanation
Correct answer: A. 12 h
- Step 1: In one hour they fill 1/30 + 1/20 = 1/12 of the tank.
- Step 2: So the time is the inverse: 12 hours.
Answer
12 h.
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