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    Question

    Tap P can fill a water tank in 15 minutes, Tap Q can fill it in 20 minutes, and Tap R can empty half of the tank in 15 minutes. Now, if all the taps, P, Q, and R, are opened simultaneously, with the unique ability that Tap R starts to empty the tank after the first minute, how long will it take to completely fill the water tank

    A 15 min Correct Answer Incorrect Answer
    B 25 min Correct Answer Incorrect Answer
    C 12 min Correct Answer Incorrect Answer
    D 10 min Correct Answer Incorrect Answer
    E none of these Correct Answer Incorrect Answer

    Solution

    ATQ, Time taken by Tap R to empty the full tank = 15 × 2 = 30 minutes Let the total capacity of Water tank = 60 litres (LCM of 15, 20 and 30) Quantity of water tank filled by Tap P in one minute = 60/15 = 4 litres Quantity of water tank filled by Tap Q in one minute = 60/20 = 3 litres Quantity of water tank emptied by Tap R in one minute = 60/30 = 2 litres Hence Required time taken = {60/(4 + 3 - 2)} = 12 minutes

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