Since I lead this on a slight tangent I will get back on topic:
When I learned averages and percentages in school I was excited to finally know what a batting average actually meant. I remember trying to figure out how often someone got a hit out of how often he had an AB and being surprised that it matched up with the BA.
Had I had a teacher that used the backs of cards to teach me math, maybe I wouldn't have been so surprised that BA wasn't just a made up number. Now if only someone could explain the math behind WAR. haha