It's 7:45 PM on Friday night. I'm with my last tutee of the week. She's a very bright girl and catches on quick, but at the most inexplicable times, she has these senior moments that make me smack my forehead.
Me: Now all you have to do is simplify the radical. The square root of 144 is.....?
Student: 15! 18! 16!
Me: Dude, you are saying every number EXCEPT the correct answer.
Student: (pause) 12?
Me: Yes! Finally!