Answer:Train A is 90 m long and running at 72 km/h.
Train B is 120 m long and running at 36 km/h.
When the trains are running in opposite directions, their relative speed gets added: 72+36 = 108 km/h.
The total length of A and B = 90+120 = 210 m
So the time taken to cross each other = 210 m*60*60/108*1000m
= 7 seconds
Explanation:
