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    Question

    Ratio of speed of a boat in still water to speed of stream

    is 9:1 respectively.Ratio of the time taken by the boat to cover a distance of (x + 50) km upstream and (x – 70) km in downstream is 15:11 respectively. Find the value of x.
    A 1556 Correct Answer Incorrect Answer
    B 1390 Correct Answer Incorrect Answer
    C 1520 Correct Answer Incorrect Answer
    D 1440 Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    ATQ,

    Let speed of boat in still water and speed of stream is ‘9a’ km/h and ‘a’ km/h respectively.

    Upstream speed = 9a – a = 8a km/h

    Downstream speed = 9a + a = 10a km/h

    So, [(x + 50)/8a]/[(x – 70)/10a] = 15/11

    Or, 11(x + 50) = 12(x – 70)

    Or, 11x + 550 = 12x – 840

    Or, x = 1390

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