Question

    200 metre long train lsquo;Arsquo; is running with a

    speed of 72 km/hr. Train lsquo;Brsquo; which is 290 metre long is running with a speed of 90 km/h in opposite direction of train lsquo;Arsquo;. For how much time, the smaller train is completely obscured by the larger train when they cross each other?
    A 2 second Correct Answer Incorrect Answer
    B 1 second Correct Answer Incorrect Answer
    C 6 second Correct Answer Incorrect Answer
    D 3 second Correct Answer Incorrect Answer
    E 4 second Correct Answer Incorrect Answer

    Solution

    Length of smaller train = 200 metre Speed of smaller train = 72 times; (5/18) = 20 m/s Length of bigger train = 290 metres Speed of bigger train = 90 times; (5/18) = 25 m/s Since, the smaller train is completely obscured by larger train, therefore, extra length of larger train = 290 ndash; 200 = 90 metres Relative speed of trains lsquo;Arsquo; and lsquo;B lsquo;= 20 + 25 = 45 m/s (Since, the trains are running in opposite direction) Required time = 90/45 = 2 second

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