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    Question

    A boat’s speed in still water is to the stream’s speed

    as 7:2. If the boat covers 50.4 km downstream in 96 minutes, find its upstream speed.
    A 11.11 km/h Correct Answer Incorrect Answer
    B 15.5 km/h Correct Answer Incorrect Answer
    C 24.9 km/h Correct Answer Incorrect Answer
    D 17.5 km/h Correct Answer Incorrect Answer

    Solution

    ATQ,

    Let the speed of boat in still water and speed of stream be 7v and 2v km/h respectively.

    So, (7v + 2v) × (96/60) = 50.4

    Or, 9v × 1.6 = 50.4

    Or, 9v = 31.5

    Or, v = 3.5

    Therefore, upstream speed = 7v - 2v = 5v = 5 × 3.5 = 17.5 km/h

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