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    Question

    A train crosses a 500-metre-long platform in 30 seconds,

    and the same train crosses a tunnel 20% longer than the platform in 42 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
    E None of these 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 + 500)/30 = (l + 600)/42
    7l + 3500 = 5l + 3000
    l = 250
    l = 250 metres
    x = (l + 500)/30 = 750/30 = 25 m/s = 25×(18/5) = 90 km/h

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