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    Question

    A alone can complete 50% of a work in 15 days while B

    takes 10 days more than A to complete it. If B and C together can complete the work in 20 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 42 days Correct Answer Incorrect Answer

    Solution

    Time taken by A alone to complete the entire work = 15/0.5 = 30 days Time taken by B alone to complete the entire work = 30 + 10 = 40 days Let the total work = L.C.M of 30, 40 and 20 = 120 units Then, efficiency of B = (120/40) = 3 units/day Combined efficiency of B and C = (120/20) = 6 units/day So, efficiency of C alone = 6 – 3 = 3 units/day So, time taken by C alone to complete the entire work = (120/3) = 40 days

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