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    Question

    A train crosses a 300-metre-long bridge in 20 seconds,

    and the same train crosses a tunnel twice the length of the bridge in 35 seconds. Find the speed of train in km/h.
    A 72 km/hr Correct Answer Incorrect Answer
    B 75 km/hr Correct Answer Incorrect Answer
    C 66 km/hr Correct Answer Incorrect Answer
    D 60 km/hr Correct Answer Incorrect Answer

    Solution

    Let the length and speed of train be ‘l’ metres and ‘x’ m/s, respectively.
    Then, according to question,
    (l + 300)/20 = (l + 600)/35
    7l + 2100 = 4l + 2400
    3l = 300
    l = 100 metres
    x = (l + 300)/20 = 400/20 = 20 m/s = 20×(18/5) = 72 km/h

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