Two trains 140 m and 160 m long run at the speed of 60 km/hr and 40 km/hr respectively in opposite directions on parallel tracks. The time which they take to cross each other, is

Correct Answer : B.

Relative Speed = 60+40 = 100 kmph
= 100*(5/18) = 250/9 m/sec
Distance = 140+160 = 300 meters
Time = Distance/Speed
$$\begin{gathered} 300\times \frac{9}{250}=\frac{54}{5} \\ =10.8 seconds \end{gathered}$$
So the time trains will take to cross each other will be 10.8 seconds