Just as I was leaving the school building I saw a fellow teacher from my previous school. She was there to attend an after-school meeting at my new school. We talked genially and briefly, and then, as she went to the doorway to go to the meeting inside, we discovered the door had locked behind me when I came out. We tugged on the door, and I wondered which door out of all the doors in my, new, huge school would provide access to the meeting inside.
Suddenly, one of my math students still on the grounds, Jake, yells out, "Hey! Mr. W! Area and perimeter!"
I yell back, "Circumference!"
Then I thought, "Wait a minute. Jake has been going to this school a long time. He'll know how to get into the building."
So I yell out, "Jake! How do you get into the school building?"
Jake yells back, "Try the door!"
Me: "And so now you can see that pizza sizes are based on the diameter, not the radius or the circumference. So when you order a pizza, what do you do? Charlotte."
Charlotte: "Call Pizza Hut and tell 'em you want a pizza."