Question

Pipe P and Q can fill a tank in 20 minutes and 30 minutes individually. Another pipe R can empty the tank in 60 minutes. When all the three pipes are opened together then What will be the time taken by them to fill 75% of the capacity of the tank.

A 12 minutes Correct Answer Incorrect Answer
B 12.20 minutes Correct Answer Incorrect Answer
C 10 minutes Correct Answer Incorrect Answer
D 11.25 minutes Correct Answer Incorrect Answer
E none of these Correct Answer Incorrect Answer

Solution

ATQ, we can say that The capacity of the tank be = 60 units So, Part of the tank filled by P in 1 minute is = 3 units  So, Part of the tank filled by Q in 1 minute = 2 units  Therefore, Part of the tank emptied by R in 1 minute = 1 unit  So, Part of the tank filled by P, Q and R in 1 minute = 4 units Hence, the Required time  will be = [(¾)  x  60  x (¼)] = 11.25 minutes

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