289. Automobile Wheels. "You see, sir," said the car salesman, "the front wheel of the car you are buying makes 4 more revolutions than the rear wheel every 360 feet; but if you were to reduce the circumference of each wheel by 3 feet, the front wheel would make 6 more revolutions than the rear wheel over the same distance."

Why the buyer did not want the difference in the number of revolutions to increase is not our concern. The puzzle is to find the circumference of each wheel. This is very easy to do.
289. The circumferences of the front and rear wheels are 15 and 18 feet, respectively. Thus, every 360 feet, the front wheel makes 24 revolutions, and the rear wheel makes 20 revolutions, with a difference of 4 revolutions. If the circumference length is reduced by 3 feet, then 12 will fit 30 times in 360 feet, and 15 will fit 24 times, and the difference will be 6 revolutions.