Me: Sam, can you finish the table for us?
Sam: Just a sec. <Fumbles with calculator> Almost there. No, that's not right.
Me: <Smiling and waving my marker by the board>
Sam: <With focus> The values are 2, 1, 0, and -1. Oh! Those are the same values we have already.
Class: We were wondering how long it was going to take you to get the answer!