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    Question

    A boat travels from point 'Y' to point 'Z' downstream

    and then returns to point 'X', which is located midway between 'Z' and 'Y'. The entire trip takes 11 hours. The distance between points 'Y' and 'Z' is 150 km. If the boat's speed in still water is three times the speed of the stream, determine how long it will take the boat to travel 180 km upstream.
    A 18 hours Correct Answer Incorrect Answer
    B 13.2 hours Correct Answer Incorrect Answer
    C 16 hours Correct Answer Incorrect Answer
    D 15.5 hours Correct Answer Incorrect Answer
    E 10 hours Correct Answer Incorrect Answer

    Solution

    Let stream speed = s Boat speed in still water = 3s Downstream speed = 4s, Upstream speed = 2s Time: 150/(4s) + 75/(2s) = 11 => 37.5/s + 37.5/s = 11 => 75/s = 11 => s = 75/11 Upstream speed = 2s = 150/11 Time for 180 km upstream = 180 / (150/11) = 66/5 = 13.2 hours

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