I'm glad you get a kick out of it!
It wasn't until I started browsing the forums associated with xkcd that I learned that each comic has a "mouseover." That is, if you view the comics on their website and hover your mouse pointer on it for a while, the text that appears adds to the joke in some way.
g
Humor?
Humor?
My wife and I are going to see the Bourne Ultimatum tonight and, well, I'm sorry, I couldn't resist this lame math humor.
-g
-g