Two trains are moving in opposite directions with speeds of 35 m/s and 45 m/s respectively. From the time they are 12 km apart, how much time would they take to cross each other?

2 minutes 30 seconds

Relative speed ( when they moves in opposite direction ) = 35 + 45 = 80 m/sec

Distance to be covered = 12 km = 12000 m

Speed = \(\frac{Distance}{Time}\)

= \(\frac{12000}{80}\)

= 150 sec

= 2 minutes 30 seconds