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    Question

    Train 'A' takes 25 seconds to pass a stationary pole and

    32 seconds to cross a bridge that is 112 meters long. When moving in opposite directions, train 'A' crosses train 'B' in 20 seconds. If train 'B' has a length of 200 meters, determine its speed.
    A 14 m/s Correct Answer Incorrect Answer
    B 20 m/s Correct Answer Incorrect Answer
    C 54 m/s Correct Answer Incorrect Answer
    D 18 m/s Correct Answer Incorrect Answer

    Solution

    Distance covered by train 'A' in 25 seconds = length of train 'A'

    Distance covered by train 'A' in 32 seconds = length of train 'A' + 112 metres

    So, distance covered by train 'A' in (32 - 25) i.e. 7 seconds = 112 metres

    So, speed of train 'A' = 112 ÷ 7 = 16 m/s

    Length of train 'A' = 16 X 25 = 400 metres

    Let the speed of train 'B' = 'x' m/s

    When travelling in opposite directions, relative speed of train 'A' w.r.t train 'B' = (16 + x) m/s

    We have, (400 + 200) ÷ (16 + x) = 20

    (16 + x) = 600 ÷ 20 = 30

    So, x = 30 - 16 = 14

    Therefore, speed of train 'B' = 14 m/s

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