Question

    The lengths of trains 'P' and 'Q' are 180 metres and 120

    metres respectively. Train 'P' crosses a platform 'Y' of 240 metres in 24 seconds. If 'P' and 'Q' cross each other while moving in opposite directions in 12 seconds, then find the time taken by 'Q' to cross the platform 'Y'.
    A 25 secs Correct Answer Incorrect Answer
    B 32 secs Correct Answer Incorrect Answer
    C 18 secs Correct Answer Incorrect Answer
    D 48 secs Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    ATQ,

    Let the speed of 'P' be 'x' m/sec So, total distance covered by 'P' while crossing the platform = (180 + 240) = 420 metres ATQ, 420 = x × 24 So, x = 17.5 m/sec Let the speed of 'Q' be 'y' m/sec Relative speed of 'P' with respect to 'Q' = (x + y) = (17.5 + y) m/sec Total distance = 180 + 120 = 300 metres ATQ, 300 = (17.5 + y) × 12 => 17.5 + y = 25 => y = 25 - 17.5 = 7.5 m/sec So, time taken by 'Q' to cross the platform = (120 + 240) ÷ 7.5 = 360 ÷ 7.5 = 48 seconds

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