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    Question

    A alone can complete 50% of a work in 10 days while B

    takes 8 days more than A to complete it. If B and C together can complete the work in 12 days, then find the time taken by C alone to complete the same work.
    A 30 days Correct Answer Incorrect Answer
    B 40 days Correct Answer Incorrect Answer
    C 24 days Correct Answer Incorrect Answer
    D 21 days Correct Answer Incorrect Answer

    Solution

    Time taken by A alone to complete the entire work = 10/0.5 = 20 days Time taken by B alone to complete the entire work = 20 + 10 = 30 days Let the total work = L.C.M of 20, 30 and 12 = 420 units Then, efficiency of B = (420/28) = 15 units/day Combined efficiency of B and C = (420/12) = 35 units/day So, efficiency of C alone = 35 – 15 = 20 units/day So, time taken by C alone to complete the entire work = (420/20) = 21 days

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