Multiple choice

A train running with speed 70 km/h can cross another train which length is (\frac{1}{3})rd of the first train, running in opposite direction in 14.4 seconds. If the speed of second train is 56 km/h, then find the time in which they will cross each other running in same directions.

  1. 136.6 seconds

  2. 129.6 seconds

  3. 99.6 seconds

  4. 106 seconds
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Opposite direction: relative speed = 70 + 56 = 126 km/h = 35 m/s. Distance = (L + L/3) = 4L/3. Time = 14.4s, so 4L/3 = 35 × 14.4, giving L = 378 m. Same direction: relative speed = 70 - 56 = 14 km/h = 35/9 m/s. Time = 4L/3 ÷ 35/9 = 129.6 seconds. This is a standard relative speed application.

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