I am in fourth grade, in a "gifted and talented (GT for short)" class. During a critical thinking exercise, the teacher asks us the question, "Which weighs more - a pound of gold or a pound of feathers?" Immediately, I respond with the gold. I'm not the only one who says this, but the teacher then asks us to really think about it, "Are you sure?"
Then it hits me - duh. A pound is a pound. They weigh the same, and I am really embarrassed.