Question

    The speed of a boat in still water is 200% higher than

    the speed of stream. If the boat takes 4 hours to cover 96 km downstream, find the time it will take to cover 72 km upstream.
    A 2 hrs Correct Answer Incorrect Answer
    B 8 hrs Correct Answer Incorrect Answer
    C 6 hrs Correct Answer Incorrect Answer
    D 12 hrs Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    ATQ,

    Let the speed of stream be 'y' km/h.

    So, speed of boat in still water = 3y km/h

    Downstream speed of boat = 3y + y = 4y km/h

    So, 4y = (96/4)

    Or, 'y' = 6

    Upstream speed of boat = 3y - y = 2y = 2 × 6 = 12 km/h

    Therefore, required time = (72/12) = 6 hours

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