Not too long ago, my college-algebra students and I were chatting about graphing polynomials. At one point during our lesson, I quickly drew a smooth, wavy curve on the board and asked,
"How many roots would a polynomial with this graph have? Five? It crosses the x-axis five times."
Students: Um, it's not six?
Me: What? Oh, yes. Six. I missed one. Listen, on that note, let me give you some advice, okay? This is serious, and you should take this with you for the rest of your life. So please pay attention.
[looks students in their eyes]
There are only two --- NO shoot! It's three.... --- there are only THREE types of people in the world.
[ineffectively pauses for effect]
Those who can count.
Those who cannot.
Students: [stare blankly]
Student #1: What?
Student #2: [leans over to Student #1 and whispers] I think she's saying she can't count.
Apparently I can neither count NOR tell jokes about counting (the comic below might be relevant), but the rest of the lecture was great. And I bought two -- not three, heh -- fancy cupcakes afterwards, so I'd say everything turned out just fine.