SPLOTT!!! That's it! As soon as I saw your post I remembered the whole thing. Thanks!
I'd do it on the board and these rough-edged teens would alternately try to explain how I was wrong and laugh their asses off as I "proved" I wasn't. Granted it was dumb. But you needed stuff like that and I had great success with kids who hated math.
Teachers must provide content but in today's world if you're not as entertaining as MTV, don't expect results.
Spaw