Here I am tinkering with Google Maps again.
My workouts during the indoor season are based on 200 meter split times (since most indoor tracks are 200 meters around), but our local track is only 160 meters around. So if I wanted to be running a 35 second 200, what would I have to run 160 in?
You have here a math teacher who applied proportional reasoning to his own life, who recognized what he was doing, and who then took steps to reconfigure that experience into a task so that his students could experience and resolve the same dilemma.
Math teachers use math. Our challenge is to preserve those experiences for our students.