Multiple choice

A train crosses a pole and bridge 200 meter long in 20 second and 30 second respectovely .how long will the train take to cross a plateform 400 meter long?

  1. 20 sec

  2. 30 sec

  3. 40 sec

  4. 45 sec

  5. 50 sec
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let train length be L meters. Speed = distance/time. Crossing pole: speed = L/20 m/s. Crossing bridge: speed = (L+200)/30 m/s. Equating: L/20 = (L+200)/30, giving 30L = 20L + 4000, so L = 200m. Speed = 200/20 = 10 m/s. Time for 400m platform = (200+400)/10 = 60 seconds... Wait, let me recalculate. Actually: L/20 = (L+200)/30 means 3L = 2L + 400, so L = 400m. Speed = 400/20 = 20 m/s. Time for platform = (400+400)/20 = 40 seconds.

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