Say something smart in the comments about why kids forget “little” things on problems. Or, alternatively, disagree with the premise of my first question. (How’s that for a lousy prompt?)
Thanks to Mark Kingsbury for the submission!
What made this question hard for the student? How come they got it wrong? Why did the student get it wrong in this particular way?
Today’s submission comes from Tina Cardone, who blogs at Drawing On Math.
The proof above isn’t great. In the comments, take on any of the following questions (or any others):