Multiple choice

A train speeds past a pole in 15 seconds and a platform 100 m long in 25 seconds. Its length is

  1. 50 m

  2. 150 m

  3. 200 m

  4. Data inadequate
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let train length be L and speed be v. L = 15v. (L + 100) = 25v. Substituting L: 15v + 100 = 25v, so 10v = 100, v = 10 m/s. L = 15 * 10 = 150 m.

AI explanation

Let the train's length be L meters and its speed be S m/sec. Passing a pole gives the equation L equals 15S. Passing the 100 m platform gives L plus 100 equals 25S. Substituting the first equation into the second yields 15S plus 100 equals 25S, meaning 10S equals 100 and S is 10 m/sec. The train's length is therefore 15 multiplied by 10, which is 150 meters.

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