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Q: A train passes two persons who are walking in the opposite direction of the train at the rate of 4 m/s and 10 m/s in 10 seconds and 8 seconds respectively. What is the speed of the train?
  • A. 10 m/s
  • B. 20 m/s
  • C. 15 m/s
  • D. 40 m/s
Correct Answer: Option B - If a train crosses a person either in same or in opposite direction the train covers the same distance which is equal to the length of the train. According to the question, Let the speed of the train = x m/sec then, (x +4) × 10 = (x + 10) × 8 5x + 20 = 4x + 40 x = 20 m/sec So, the speed of the train is 20m/sec.
B. If a train crosses a person either in same or in opposite direction the train covers the same distance which is equal to the length of the train. According to the question, Let the speed of the train = x m/sec then, (x +4) × 10 = (x + 10) × 8 5x + 20 = 4x + 40 x = 20 m/sec So, the speed of the train is 20m/sec.

Explanations:

If a train crosses a person either in same or in opposite direction the train covers the same distance which is equal to the length of the train. According to the question, Let the speed of the train = x m/sec then, (x +4) × 10 = (x + 10) × 8 5x + 20 = 4x + 40 x = 20 m/sec So, the speed of the train is 20m/sec.