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Discussion

  1. A train 400 m long is running at a speed of 54 km/hr. If it crosses a tunnel in 2 minutes. Then what is the length of tunnel?
    1. 1200 m
    2. 1400 m
    3. 1600 m
    4. 1800 m
  1. Correct Option: B

    Speed of train in m/sec = (speed of train in km/hr) x 5/18

    ∴ speed of train in m/sec = 54 x 5/18 = 15 m/sec

    Time taken to cross the tunnel = 2 minutes = 120 sec

    Therefore, Total length covered by train in crossing the tunnel = Speed of train x Time taken to cross the tunnel

    = 15 m/sec x 120 sec = 1800 m

    Now, we know that
    Total length covered by train in crossing the tunnel = Length of train + Length of tunnel

    Given, Length of train =400m and
    Calculated above, Length covered by train in crossing the tunnel = 1800 m

    Therefore, Length of tunnel = 1800m- 400m = 1400m




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