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    Question

    Two trains X and Y are running in opposite directions.

    The speed of train X is x m/s and that of train Y is (x – 20) m/s. The lengths of trains X and Y are 160 m and 200 m respectively. They cross each other in 9 seconds. Find the sum of the time taken by train X to cross a 140 m platform and train Y to cross a pole.
    A 13 secs Correct Answer Incorrect Answer
    B 30 secs Correct Answer Incorrect Answer
    C 15 secs Correct Answer Incorrect Answer
    D 23 secs Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    ATQ, Total distance covered while crossing each other = 160 + 200 = 360 m Relative speed = x + (x – 20) = 2x – 20 m/s So, 360 = (2x – 20) * 9 360/9 = 2x – 20 40 = 2x – 20 2x = 60 x = 30 m/s Speed of train X = 30 m/s Time taken by train X to cross a 140 m platform = (160 + 140) / 30 = 300 / 30 = 10 seconds Speed of train Y = x – 20 = 30 – 20 = 10 m/s Time taken by train Y to cross a pole = length of Y / speed = 200 / 10 = 20 seconds Required sum = 10 + 20 = 30 seconds

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