Ok, since reading Shamus's oldie-but-goodie brain-bender, I thought I'd offer this one. It really works better if you're there to say it out loud, but we'll try it here.
First, draw this on a piece of paper, then ask: "How can you change this to nine-fifty by just adding one line?"
First, draw this on a piece of paper, then ask: "How can you change this to nine-fifty by just adding one line?"