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    Question

    The downstream and upstream speeds of a boat are 36 km/hr

    and 28 km/hr, respectively. If the boatman covers (x + y) km upstream in 8 hours while the stream flows at double its usual speed, find the average of x and y.
    A 96 km Correct Answer Incorrect Answer
    B 60 km Correct Answer Incorrect Answer
    C 73 km Correct Answer Incorrect Answer
    D 85 km Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    ATQ,

    Let, speed of boat in still water and stream speed be B km/hour and s km/hour, respectively.

    So, (B + s) = 36 … (i)

    Also, (B – s) = 28 … (ii)

    Solving equation (i), and (ii), we get,

    B = 32 km/hour

    s = 4 km/hour

    According to question,

    (x + y)/(B – 2s) = 8

    (x + y) = 8 × (32 – 2 × 4) = 8 × 24 = 192 km

    Therefore, average value of x and y = (x + y)/2 = 192/2 = 96 km

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