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    Question

    A train takes 30 seconds to pass a 500-metre-long bridge

    and takes 40 seconds to cross a tunnel that is 50% longer than the bridge. Find the speed of the train in km/h.
    A 90 km/h Correct Answer Incorrect Answer
    B 45 km/h Correct Answer Incorrect Answer
    C 30 km/h Correct Answer Incorrect Answer
    D 75 km/h Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    ATQ,

    Let the length and speed of train be ‘l’ metres and ‘x’ m/s, respectively.

    Then, according to question,

    (l + 500)/30 = (l + 750)/40

    40(l + 500) = 30(l + 750)

    40l + 20000 = 30l + 22500

    10l = 2500

    l = 250 metres

    x = (l + 500)/30 = 750/30 = 25 m/s = 25 × (18/5) = 90 km/h

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