answer:10 seconds.

reason:3600*(1/6)*60 10

Lets Make Thinks clear..

1. Its obvious that since the trains travel towards each other the speed is 60+60 miles/hr

2. The two trains will take 2/6 miles to cross themselves since the length of the train is 1/6 miles.

3. If it is 3600 sec for 120 miles then x sec for 2/6 miles

Therefore 120/3600 (2/6)/x

x 10 sec.

Hi

I am doing B.E IIyr.I ve doubt how come you could say that the velocity is 120mile/hr......actually it appears to be twice the velocity of each but actually.....so are you trying to say at the time of crossing the train moves at 120mile/hr once they get crossed they again go to 60mile/hr.how come this is possible ..........would you explain me this concept........