Coin rotation paradox

Earth has 365 days in a year, but actually rotates 366 times. The extra rotation comes from its orbit around the Sun — an example of the coin rotation paradox.

In the 1982 SAT, only 3 of 300,000 students answered a circle rotation problem correctly. Even the test makers were wrong, and the correct answer was not among the choices. The key is the coin rotation paradox: a circle rolling around an equal circle makes 2 full turns, not 1.