A tank can be filled by Pipe A in 5 hours and Pipe B in 10 hours, while Pipe C empties it in 20 hours. If all three are opened together, how long to fill the tank?
A4 hours
B4.4 hours
C5 hours
D5.5 hours
Explanation
Net rate = 1/5 + 1/10 – 1/20 = (4 + 2 – 1) / 20 = 5 / 20 = 1/4 per hour. Time required = 4 hours.
Exam Relevance
- Topic: Work and Time
- Subtopic: Pipes and Cisterns
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