A train leaves a station and travels north at 50km/hr. FourFour hours later, a second train leaves on a parallel track and travels north at 90km/hr. How far from the station will they meet?
Four hours later means the second train must catch up 50*4=200 km. The difference in speed is (90-50)=40 km/hour. Time to catch up = 200 km/40 km/hour = 5 hours.
