Two trains are running in opposite directions in the same speed. The length of each train is 120 meter. If they cross each other in 12 seconds, the speed of each train (in km/hr) is

Distance covered = 120+120 = 240 m
Time = 12 s
Let the speed of each train = x.
Then relative velocity = x+x = 2x
2x = distance/time = 240/12 = 20 m/s
Speed of each train = x = 20/2 = 10 m/s
= 10*18/5 km/hr = 36 km/hr