Multiple choice

A train moves past a metal board in 20 sec and a station 300 m long in 50 sec. Its length and speed are:

  1. 100 m, 20 m/sec

  2. 200 m, 10m/sec

  3. 105 m, 10m/sec

  4. 200 m, 20 m/sec

  5. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let train length = L and speed = S. When passing a metal board (considered a point), time = L/S = 20 seconds, so L = 20S. When passing a 300m station, time = (L+300)/S = 50 seconds. Substituting L = 20S: 20S + 300 = 50S, which gives 300 = 30S, so S = 10 m/s and L = 200m.

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