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    Question

    Train A and B can cross a 400 meters long platform in

    the same time. The length of Train A is 480 meters and the speed of Train B is twice the speed of Train A. If Train A crosses a bridge of the same length as of Train B in 40 seconds, then find the time (in seconds) taken by Train B to cross a tunnel 20 m long.
    A 12 Correct Answer Incorrect Answer
    B 15 Correct Answer Incorrect Answer
    C 18 Correct Answer Incorrect Answer
    D 20 Correct Answer Incorrect Answer
    E 16 Correct Answer Incorrect Answer

    Solution

    Let speed of train A = v meters/second
    And speed of train B = 2v meters/second
    Let length of train B = y meters ATQ, (y + 400)/2v = (480 + 400)/v
    y + 400 = 1760
    y = 1360 meters Speed of train A = (480 + 1360)/40 = 46 m/sec
    Speed of train B = 2 × 46 = 92 m/sec Required time = (1360 + 20)/92 = 15 sec

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