Multiple choice

Two trains $200\ m$ long each are moving towards each other.The first train has speed of $15$ m/sec while the second train has speed of $25$ m/sec. How long will they take to cross each other?

  1. $8$sec
  2. $13.5$ sec
  3. $12$ sec
  4. $10$ sec
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D Correct answer
Explanation

Relative speed = 15 + 25 = 40 m/s. Total distance to cover = 200 + 200 = 400 m. Time = Distance / Relative Speed = 400 / 40 = 10 seconds.

AI explanation

Since the trains are moving towards each other, their relative speed is the sum of their speeds, giving 15 m/sec plus 25 m/sec equal to 40 m/sec. The total distance to be covered for them to cross each other is the sum of their lengths, giving 200 m plus 200 m equal to 400 m. Using the time formula where time equals distance divided by speed, the time taken is 400 m divided by 40 m/sec, which results in 10 sec.

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