I filled up my Prius's gas tank tonight; a while later, on the way home from the East Bay, I noticed that the MPG indicator (showing miles per gallon since the most recent gas-tank fill-up) said I was getting 50 miles per gallon, and the odometer (which appears right next to the MPG indicator) said I had gone 51 miles.
Neat, I thought to myself. The MPG indicator has nearly caught up to the odometer. I wonder what gas mileage I would need to get in the next few minutes for the MPG indicator to pass the odometer—that is, for the display to show a number on the MPG indicator that's greater than the number showing at the same time on the odometer. (Not just greater than 51; greater than whatever the odometer will say at that future time.)
It didn't take long to figure out the answer, but I think it's kind of a neat puzzle, and thought some of you might enjoy it.