Question

Pipe A and B can fill the pool in 15 minutes and 20 minutes, respectively. Pipe C can empty half filled pool in 6 minutes. If all the pipes are opened together, then find the time taken to fill the empty pool completely

A 20 minutes Correct Answer Incorrect Answer
B 21 minutes Correct Answer Incorrect Answer
C 30 minutes Correct Answer Incorrect Answer
D 15 minutes Correct Answer Incorrect Answer

Solution

Time taken by pipe C to empty the full pool = 6 × 2 = 12 minutes Let the capacity of pool = 60 units Number of units of water filled by pipe A alone in one minute = 60/15 = 4 units Number of units of water filled by pipe B alone in one minute = 60/20 = 3 units Number of units of water emptied by pipe C alone in one minute = 60/12 = 5 units Required time taken = 60/(4 + 3 – 5) = 30 minutes

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