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    Question

    A train with 18 compartments of equal length takes 36

    seconds to cross a pole and 45 seconds to cross a 180-metre-long platform. If 9 compartments are removed, how long would it take to cross a pole?
    A 20 seconds Correct Answer Incorrect Answer
    B 22 seconds Correct Answer Incorrect Answer
    C 18 seconds Correct Answer Incorrect Answer
    D 16 seconds Correct Answer Incorrect Answer
    E 21 seconds Correct Answer Incorrect Answer

    Solution

    Let the original length of the train = ‘d’ metres
    Then, distance covered by the train in 36 seconds = ‘d’ metres
    Distance covered by the train in 45 seconds = (d + 180) metres
    So, distance covered in (45 – 36) = 9 seconds = (d + 180 – d) = 180 metres
    So, speed of the train = 180 ÷ 9 = 20 m/s
    So, original length of the train = 20 × 36 = 720 metres
    After removing 9 compartments, length of the train = 720 × (9/18) = 360 metres
    So, required time taken = 360 ÷ 20 = 18 seconds

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