In contrast to the crystallized approach to solving the problem, Horn provided an example of a fluid approach to solving the problem that does not depend on the learning of high school level algebra. Horn invented a boy who is too young to attend secondary school but could solve the problem through the application of fluid ability: "He may reason that, if half the two-legged people are without shoes, and all the rest (an even number) are one-legged, then the shoes must average one per person, and the answer is 100."