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    Question

    Train 'R' can cross a pole in 6 seconds and a 240 metres

    long bridge in 10 seconds. Train 'S' whose length is 75% of the length of train 'R' runs in the same direction of train 'R'. If train 'S' crosses train 'R' in 14 seconds, then find the speed of train 'S'.
    A 100 m/s Correct Answer Incorrect Answer
    B 105 m/s Correct Answer Incorrect Answer
    C 110 m/s Correct Answer Incorrect Answer
    D 115 m/s Correct Answer Incorrect Answer
    E 120 m/s Correct Answer Incorrect Answer

    Solution

    Let the length and the speed of the train 'R' be 'x' metres and 's' m/s.
    ATQ,
    (x/s) = 6
    So, 'x' = 6s.........(i)
    Also, {(x + 240) ÷ s} = 10
    Or, 6s + 240 = 10s [from equation (i)]
    Or, 240 = (10s - 6s)
    Or, 's' = (240/4) = 60
    Length of train 'R' = (6 × 60) = 360 metres
    So, length of train 'S' = (360 × 0.75) = 270 metres
    Let the speed of train 'S' be 't' m/s.
    ATQ,
    (360 + 270) ÷ (t - 60) = 14
    Or, 630 = 14 × (t - 60)
    Or, (t - 60) = 45
    So, 't' = 45 + 60 = 105
    Therefore, speed of train 'S' = 105 m/s

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