Multiple choice

A 100 m long train is running at a speed of 86 km/hr towards another train, which is running at a speed of 64 km/hr. If the trains are 875 m apart, in how much time will they meet while running in opposite directions?

  1. 6 sec.

  2. 15 sec.

  3. 21 sec.

  4. 40 sec.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Trains running in opposite directions have relative speed = 86 + 64 = 150 km/hr = 150 × (5/18) = 41 2/3 m/s. Distance = 875 m. Time = 875 ÷ (125/3) = 875 × 3/125 = 21 seconds. Alternatively: 150 km/hr = 150000 m/3600 s = 125/3 m/s, so time = 875/(125/3) = 21s.

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