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    Question

    The speed of a boat in still water is to the speed of

    the stream in the ratio 9:4, respectively. The total time taken by the boat to cover a distance of Q km upstream and the same distance downstream is 65 hours. Find the time required to cover (3Q/5) km downstream.
    A 10 hrs Correct Answer Incorrect Answer
    B 18 hrs Correct Answer Incorrect Answer
    C 15 hrs Correct Answer Incorrect Answer
    D 21 hrs Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    ATQ,

    Let the speed of boat in still water and speed of stream be 9x km/h and 4x km/h respectively. So, speed of boat downstream = 9x + 4x = 13x km/h Speed of boat upstream = 9x - 4x = 5x km/h According to the question: (Q/5x) + (Q/13x) = 65 Or, Q × (18/65x) = 65 Or, Q = 325x Required time = (3/5 × 325x)/13 = 15 hours

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