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    Question

    Two inlet pipes 'C' and 'D' can fill a tank in 18 minutes

    and 27 minutes respectively. Both are opened together. After the tank is half full, a leak develops which removes (2/5) of the incoming water. Find the total time to fill the tank.
    A 13.4 minutes Correct Answer Incorrect Answer
    B 14.4 minutes Correct Answer Incorrect Answer
    C 15.2 minutes Correct Answer Incorrect Answer
    D 12.6 minutes Correct Answer Incorrect Answer

    Solution

    Let capacity be 162 litres (LCM of 18 and 27)
    'C' = 162 ÷ 18 = 9 litres/min
    'D' = 162 ÷ 27 = 6 litres/min
    Time to fill half = (0.5 × 162) ÷ (9 + 6) = 81 ÷ 15 = 5.4 minutes
    Effective rate after leak = (3/5) × (9 + 6) = 9 litres/min
    Time to fill remaining = (0.5 × 162) ÷ 9 = 81 ÷ 9 = 9 minutes
    Total time = 5.4 + 9 = 14.4 minutes

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