Potato paradox
Not exactly the same, but I stumbled on another seemingly confusing math reality a little while back.  It's probably obvious for places that measure their mileage in gallons/100 miles or kms or whatnot, but for MPG:<p>If you could chose to increase the average fuel economy of a car, which of these would save the most fuel:<p>1. 10mpg -> 12mpg<p>2. 12mpg -> 15mpg<p>3. 15mpg -> 20mpg<p>4. 20mpg -> 30mpg<p>5. 30mpg -> 60mpg<p>Of course with a little thought, it turns out that they all save the same amount of fuel, but it's hard to wrap my brain around the fuel savings being equal between 10mpg-12mpg and 30mpg-60mpg.