Given: The length of train A is 200 m and the speed is 90 km/h The length of train B is 160 m and the speed is 72 km/h Calculation: They are coming from the same direction, so the relative speed of them = (90 - 72) km/h ⇒ 18 km/h ⇒ {18 × (
5
18
)} m/s ⇒ 5 m/s Total distance covered by A and B = (200 + 160) m = 360 m So, to cross each other completely the required time = (
360
5
) sec = 72 sec ∴ They can cross each other completely in 72 sec.