A "Local" train leaves a station and runs at an average rate of 35 mph. An hour and a half later an "Express" train leaves the station and travels at an average rate of 56 mph on a parallel track. How many hours after the Express train starts will the it overtake the Local?
Hello,
Let's assume x the time the express runs.
56x=35(1.5+x)
==>21x=52.5
==>x=2.5 h =2 h 30 min