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    Question

    A train travelling at the speed of 72 km/hr crosses

    another train, having 20 meters less length and travelling in opposite direction at the speed of 54 km/hr in 8 seconds. If the longer train crosses a platform in 16 seconds, then the shorter train will cross the same platform in how many seconds?
    A 18 seconds Correct Answer Incorrect Answer
    B 19 seconds Correct Answer Incorrect Answer
    C 20 seconds Correct Answer Incorrect Answer
    D 21 seconds Correct Answer Incorrect Answer
    E 22 seconds Correct Answer Incorrect Answer

    Solution

    Speed of longer train = 72 × (5/18) = 20 m/s
    Speed of shorter train = 54 × (5/18) = 15 m/s

    Let length of longer and shorter trains be ‘L’ meters and (L – 20) metres, respectively.

    According to question,

    L + L – 20 = (20 + 15) × 8 = 280

    2L – 20 = 280

    L = 150 metres

    So, L – 20 = 130 metres

    Let length of platform is ‘P’ metres

    So, P + 150 = 20 × 16 = 320

    P = 320 – 150 = 170 meters

    Desired time = (170 + 130)/15 = 300/15 = 20 seconds

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