Exams › IBPS PO › Quantitative Aptitude
Two pipes A and B can fill the reservoir separately in 25 and 30 minutes respectively, but when the waste pipe is open they together can fill the reservoir in 25 minutes. What is the time taken by the waste pipe to empty the reservoir?
- 20 minutes
- 30 minutes
- 60 minutes
- 15 minutes
Correct answer: 30 minutes
Solution
Pipe A fills at \(1/25\) tank per minute and pipe B at \(1/30\). Together their filling rate is \(11/150\), but with the waste pipe open the net rate is \(1/25=6/150\). So the waste pipe empties at \(5/150=1/30\) tank per minute, meaning it takes 30 minutes to empty the tank.
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