Two taps A and B fill a tank in 12 and 15 hours. A third pipe C can empty it in 20 hours. If all three work together, how long to fill the tank?

A8 hours

B10 hours

C12 hours

D15 hours

Explanation

Rate = 1/12 + 1/15 – 1/20 = (5+4-3)/60 = 6/60 = 1/10. Time = 10 hours.

Exam Relevance

Topic: Work and Time
Subtopic: Pipes and Cisterns

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