Pipe A can fill a tank in 10 minutes. Pipe B can fill the same tank in 15 minutes. Pipe C at the bottom of the tank is a waste pipe for emptying the tank. After opening Pipe A and Pipe B, a man returns when the tank should have been full. However, he finds that Pipe C was also kept open and shuts it and the tank overflows in the next 2 minutes. How many minutes will Pipe C take to empty the tank if Pipes A and B are kept shut?
Correct Answer: Description for Correct answer:
Pipe A and Pipe B together fill \( \Large \frac{1}{10}+\frac{1}{15}=\frac{5}{30}=\frac{1}{6} \)th of the tank in a minute
Therefore, the man would have returned to the tank 6 minutes after opening the taps hoping to see the tank full. However, he finds Pipe C open and shuts it immediately.
After shutting Pipe C, the tank was full in 2 minutes.
Therefore, in the last two minutes \( \Large \frac{1}{6} \times 2=\frac{1}{3} \)rd of the tank would have been filled by Pipe A and Pipe B.
This is the quantum of water that Pipe C would have drained during the first 6 minutes.
lf Pipe C drained 1/3rd of the tank in 6 minutes, then it will take 18 minutes to drain the entire tank.
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