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Two pipes A and B can fill a tank in 45 minutes and 40 minutes respectively. They are kept open simultaneously and after some time pipe A was switched off. Pipe B fills the rest of the tank in 23 minutes after pipe A was switched off. How long was pipe A kept open?
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A) 5 minutes |
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B) 8 minutes |
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C) 6 minutes |
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D) 9 minutes |
Correct Answer:
| D) 9 minutes |
Description for Correct answer:
B alone can fill the tank in 40 mins., so if it works for 23 min it will fill \( \Large \frac{23}{40} \)th of the tank.
Remaining \( \Large \frac{17}{40} \)th of the tank has to be filled by A and B in
= \( \Large \frac{17}{40} \left[ \frac{45 \times 40}{45 + 40} \right] = \frac{17}{40} \times \frac{360}{17} \) = 9 min.
B alone can fill the tank in 40 mins., so if it works for 23 min it will fill \( \Large \frac{23}{40} \)th of the tank.
Remaining \( \Large \frac{17}{40} \)th of the tank has to be filled by A and B in
= \( \Large \frac{17}{40} \left[ \frac{45 \times 40}{45 + 40} \right] = \frac{17}{40} \times \frac{360}{17} \) = 9 min.
Part of solved Pipes and Cisterns questions and answers : >> Aptitude >> Pipes and Cisterns
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