A form of applied math usually learned in college (but outside of the classroom) that involves figuring out just how many beers from a case are rightfully yours. When splitting a case (commonly a 30 beer case of Keystone Light or Busch Light) with friends, one will usually perform a quick mental equation of the portion of the case that belongs to them.
It's been theorized that Case Math is the only form of math that's actually worth two fucks.
Ed: Just picked up a 30 rack! You, Alex, and I are splitting it.
*you and Alex quickly perform some mental case math and both deduce quickly that each guy gets 10 beers*
*Ed is trying to give a girl a beer out of the shared case, in hopes of getting her drunk and hooking up with her.*
Ed: Hey, I'm gonna give this girl a beer from our case, cool?
You: Sure, but that comes out of your beers, me and Alex are still drinking our 10. And you'd better close, too.