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    Question

    350 metre long train ‘A’ is running with a speed of

    43.2 km/hr. Train ‘B’ which is 387 metre long is running with a speed of 90 km/h in opposite direction of train ‘A’. For how much time, the smaller train is completely obscured by the larger train when they cross each other?
    A 1 second Correct Answer Incorrect Answer
    B 2 second Correct Answer Incorrect Answer
    C 3 second Correct Answer Incorrect Answer
    D 4 second Correct Answer Incorrect Answer
    E 7 second Correct Answer Incorrect Answer

    Solution

    Length of smaller train = 350 metre Speed of smaller train = 43.2 × (5/18) = 12 m/s Length of bigger train = 387 metres Speed of bigger train = 90 × (5/18) = 25 m/s Since, the smaller train is completely obscured by larger train, therefore, extra length of larger train = 387 – 350 = 37 metres Relative speed of trains ‘A’ and ‘B ‘= 12 + 25 = 37 m/s (Since, the trains are running in opposite direction) Required time = 37/37 = 1 second

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