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    Question

    P, Q, and R can complete a work in 12 days. 15 days and

    30 days, respectively, working alone. How soon can the work be completed if Q is assisted by P and R on alternate days?
    A 12 Correct Answer Incorrect Answer
    B 7 Correct Answer Incorrect Answer
    C 8 Correct Answer Incorrect Answer
    D 10 Correct Answer Incorrect Answer

    Solution

    Total work = 60 (LCM of 12, 15 and 30) P's efficiency = 60/12 = 5 Q's efficiency = 60/15 = 4 R's efficiency = 60/30 = 2 Pattern of work = PQ, QR, PQ, QR... Work done by PQ and PR in 2 days = (5 + 4) + (4 + 2) = 15 2 days = 15 units 2 × 4 = 8 days => 15 × 4 = 60 units In 8days complete total work.

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