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    Question

    Train 'X' can cross a pole in 15 seconds and a 180 metres

    long bridge in 18 seconds. Train 'Y' whose length is 80% of the length of train 'X' runs in the same direction of train 'X'. If train 'Y' crosses train 'X' in 12 seconds, then find the speed of train 'Y'.
    A 185 m/s Correct Answer Incorrect Answer
    B 190 m/s Correct Answer Incorrect Answer
    C 195 m/s Correct Answer Incorrect Answer
    D 200 m/s Correct Answer Incorrect Answer
    E 205 m/s Correct Answer Incorrect Answer

    Solution

    Let the length and the speed of the train 'X' be 'x' metres and 's' m/s.
    ATQ,
    (x/s) = 15
    So, 'x' = 15s.........(i)
    Also, {(x + 180) ÷ s} = 18
    Or, 15s + 180 = 18s [from equation (i)]
    Or, 180 = (18s - 15s)
    Or, 's' = (180/3) = 60
    Length of train 'X' = (15 × 60) = 900 metres
    So, length of train 'Y' = (900 × 0.80) = 720 metres
    Let the speed of train 'Y' be 'y' m/s.
    ATQ,
    (900 + 720) ÷ (y - 60) = 12
    Or, 1620 = 12 × (y - 60)
    Or, (y - 60) = 135
    So, 'y' = 135 + 60 = 195
    Therefore, speed of train 'Y' = 195 m/s

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