Getting There from Here
A bike messenger needs to deliver a package from the intersection of 1st Street and Arrow Avenue to the intersection of 3rd Street and Condorcet Avenue. Assuming that the messenger only travels along the roads (a big assumption!), how many different routes are possible from the one location to the other?
What if the messenger needs to go from the intersection of 1st and Arrow to the intersection of 4th and Euler? Can you generalize the formula to find the number of routes from any intersection to one which is s intersections to the South and e intersections East?