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    Question

    A train crosses a bridge in 15 secs while it crosses a

    man standing on a platform in 8 secs. If the speed of train 108 km/hrs, then what will be the time taken by the train to cross a tunnel whose length is 210 meters more than the length of the bridge .
    A 15 seconds Correct Answer Incorrect Answer
    B 20 seconds Correct Answer Incorrect Answer
    C 22 seconds Correct Answer Incorrect Answer
    D 25 seconds Correct Answer Incorrect Answer
    E none of these Correct Answer Incorrect Answer

    Solution

    ATQ, we can say that Speed of train  is = (108 x 5)/18 = 30 m/s then, the Length of bridge is = 30 x 7 = 210 m  {The "30 × 7" step comes from: Extra time over bridge = 15 − 8 = 7 sec = Bridge length = 30×7 = 210 m} then, the Length of tunnel = 210 + 210 = 420 m Length of train  108 × 5/18 = (x + 210)/15 30 × 15 = x + 210 x = 240 meter therefore, the Required time = (240 + 420)/30 = 22 seconds

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