Ed traveled 5000 miles round-trip between home and Fairbanks in a car with one spare tire. He rotated tires at intervals so that when the trip ended, each tire had been used for the same number of miles. For how many miles was each tire used?

Let’s see: 5000 miles x 4 wheels is 20,000 wheel-miles.

If there are five tires, each tire goes 4000 miles.