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    Question

    A motor boat covers a certain distance downstream in a

    river in 2 hours. It covers the same distance upstream in 2 hours and 30 minutes. If the speed of water is 1.5 km/h, then the speed of the boat in still water is:
    A 16.25 km/hr Correct Answer Incorrect Answer
    B 27 km/hr Correct Answer Incorrect Answer
    C 32.5 km/hr Correct Answer Incorrect Answer
    D 31.5 km/hr Correct Answer Incorrect Answer
    E 13.5 km/hr Correct Answer Incorrect Answer

    Solution

    Let the speed of boat in still water be x km/hr and the distance be y km. Rate downstream = (x + 1.5) km/hr Rate upstream = (x – 1.5) km/hr According to the question, y/(x + 1.5) = 2 --- (i) y/(x – 1.5) = 5/2 --- (ii) On dividing equation (i) by (ii), (x – 1.5)/(x + 1.5) = 2/(5/2) = 4/5 5x – 7.5 = 4x + 6 x = 7.5 + 6 = 13.5 kmph

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