Two trains 120 m and 180 m long run on parallel tracks in opposite directions at 50 km/h and 58 km/h. How long do they take to cross each other completely?

Explanation

1. 01

   Opposite directions: relative speed = $50 + 58 = 108$ km/$h = 30$ m/s.

2. 02

   Distance = $120 + 180 = 300$ m.

3. 03

   Time $= \frac{300}{30} = 10$ s.