A tap can fill a tank in 6 hours, while a drain pipe can empty it in 10 hours. If both are open, how long will it take to fill the tank?
A12 hours
B15 hours
C18 hours
D20 hours
Explanation
Net rate = 1/6 – 1/10 = (5 – 3) / 30 = 2 / 30 = 1/15 per hour. Time required = 15 hours.
Exam Relevance
- Topic: Work and Time
- Subtopic: Pipes and Cisterns
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