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    Question

    A man is running at a speed of 20 m/s in the same

    direction as a train. The train passes the man completely in 9 seconds. If the train's speed is 144 km/h, determine the time it will take for the train to cross a bridge that is 120 meters long.
    A 1.2 secs Correct Answer Incorrect Answer
    B 5.3 sec Correct Answer Incorrect Answer
    C 2.5 secs Correct Answer Incorrect Answer
    D 7.5 secs Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    ATQ,

    Let the length of the train be 'L' metres, Given, speed of the train = 144 km/hr = 144 X (5/18) = 40 m/sec So, the relative speed of train w.r.t the man = 40 - 20 = 20 m/sec ATQ, (L/20) = 9 So, 'L' = 180 metres Therefore, time taken by the train to cross a bridge of 120 meters: = {(180 + 120) /40} = 7.5 seconds 

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