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    Question

    A boat travels 100 km upstream and 160 km downstream in 9

    hours. If the speed of the boat in still water is 25 km/hr greater than the speed of the stream, calculate the stream's speed.
    A 4.5 km/hr Correct Answer Incorrect Answer
    B 5.5 km/hr Correct Answer Incorrect Answer
    C 1.5 km/hr Correct Answer Incorrect Answer
    D 3.5 km/hr Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    ATQ,

    Let the speed of the stream = x

    And the speed of the boat in still water = x + 25

    100/(x + 25 – x) + 160/(x + 25 + x) = 9

    100/25 + 160/(2x + 25) = 9

    4 + 160/(2x + 25) = 9

    160/(2x + 25) = 9 – 4

    160/(2x + 25) = 5

    2x + 25 = 160/5

    2x + 25 = 32

    2x = 32 – 25

    2x = 7

    x = 7 / 2

    x = 3.5

    The speed of the stream = 3.5 km/hr

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