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    Question

    'A' alone can do some work in 20 days, 'B' alone can do

    the same work in 30 days. If they work on alternate days, starting with 'B', then the work will be finished in:
    A 24 days Correct Answer Incorrect Answer
    B 25 days Correct Answer Incorrect Answer
    C 20 days Correct Answer Incorrect Answer
    D 12 days Correct Answer Incorrect Answer

    Solution

    Let the total work be 60 units {LCM (20 and 30)} So, efficiency of 'A' = 60 ÷ 20 = 3 units/day And efficiency of 'B' = 60 ÷ 30 = 2 units/day Work done in every 2 days (B + A) = 2 + 3 = 5 units So, work done in 24 days by 'A' and 'B' = (24 ÷ 2) x 5 = 60 units Total time taken = 24 days

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