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    Question

    Direction: Five workers – A, B, C, D, and E – are working on a construction project to complete 500 units of work. Each worker works different numbers of hours per day and has varying work efficiencies, which are calculated as the number of units completed per hour. The following table shows the daily working hours and the efficiency (units per hour) for each worker:

    Worker A works alone for 6 days, then Worker B joins A

    for the next 4 days, and after that, Workers C, D, and E join them. How many units of work are completed after 12 days?
    A 407.4 units Correct Answer Incorrect Answer
    B 437.8 units Correct Answer Incorrect Answer
    C 449.2 units Correct Answer Incorrect Answer
    D 453.6 units Correct Answer Incorrect Answer
    E 460 units Correct Answer Incorrect Answer

    Solution

    Total work done by A in 6 days = 6 × 8 × 2 = 96 units. Total work done by A and B in the next 4 days = (4 × 8 × 2) + (4 × 6 × 3) = 64 + 72 = 136 units. Total work done by A, B, C, D, and E in the next 2 days = (2 × 8 × 2) + (2 × 6 × 3) + (2 × 5 × 4) + (2 × 7 × 2.5) + (2 × 9 × 1.8) = 32 + 36 + 40 + 35 + 32.4 = 175.4 units. Total work after 12 days = 96 + 136 + 175.4 = 407.4 units.

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