Boat Trips
From a Dan Meyer 3-Acts lesson: http://www.101qs.com/2468
Like the Dave Major program at http://mrmeyer.com/shippingroutes/
See also a version where you need to figure out the next time both ferries are in Milwaukee together.
http://www.geogebratube.org/material/show/id/150928
Made with input from Brian Marks.