The subway train offers access to all 12 intersections downtown. If every intersection is .75 miles apart and the train travels at 20 mph and spends 45 seconds at every stop to unload and onboard new customers, how long will it take to get from the first intersection to the last intersection?
First, a couple of assumptions:
1. We ignore the consideration of how fast the train accelerates to 20 mph and how quickly its doors open
2. The clock starts when the doors open at station 1 (initiating its load/unload cycle of 45 seconds.)
The time required for the train to load/unload at station x and travel to station x+1 would then be the 45 seconds for the load/unload cycle and .75 miles / (20 miles/hour) = .0375 hours * (3600 sec/hr) = 145 sec
Thus, it takes 190 sec for a train just arrived at station x to arrive at station x+1. Since there are 11 station transits to arrive at station 12, the total time is 11*190 seconds or just shy of 34 minutes.