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    Question

    A boat takes 4 hours to travel a distance of '4D' km

    upstream. However, it covers a distance of (4D + 8) km downstream in just 2 hours. Given that the boat's speed in still water is 8 km/h, determine the value of 'D'.
    A 12 Correct Answer Incorrect Answer
    B 8 Correct Answer Incorrect Answer
    C 6 Correct Answer Incorrect Answer
    D 4 Correct Answer Incorrect Answer

    Solution

    Speed of boat in upstream = (4D/4) = 'D' km/h

    Speed of boat in downstream = {(4D + 8)/2} = (2D + 4) km/h

    So, speed of boat in still water = {(speed of boat in upstream) + (speed of boat in downstream)}/2

    So, {D + (2D + 4)}/2 = 8

    Or, 3D + 4 = 16

    Or, 3D = 12

    Or, D = 4

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