Question

    The speed of a motorboat in still water is 50 km/hr. If

    the motorboat travels 120 km along the stream in 1 hour 30 minutes, then the time taken by it to cover the same distance against the stream will be
    A 6 hours Correct Answer Incorrect Answer
    B 5hours 30 minutes Correct Answer Incorrect Answer
    C 4 hours 40 minutes Correct Answer Incorrect Answer
    D 5 hours Correct Answer Incorrect Answer
    E 7 hours 30 minutes Correct Answer Incorrect Answer

    Solution

    Let the speed of the current be x km/hr Rate Downstream = (x+ 50) km/hr According to the question  120/(x+50) = 1 hour 30 minutes 120/(x+50) = 3/2 240 = 3x + 150 x=  30 km/hr Rate upstream = 50 – 30 = 20 km/hr Required time = 120/20 = 6 hours

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