One time at my old job I was trying to load the printer, and I said something like "Oh shoot, these are oversized sheets; I need the 8.5x11."
My coworker looked at me like I was crazy. "The what?"
"The normal printer paper, the 8.5 by 11 inch paper"
"Why do you know the exact size of printer paper??"
I did not know how to respond to this question.
Ha, I'm trying to remember where I learned that as well. I know we covered it in drafting where we learned an 8.5x11 A paper is half a sheet of 11x17 B paper which is half a sheet of 17x22 C paper, and so on. But I thought I knew the size of A paper long before that, and that it was common knowledge, though I can't think of where or why I would have needed to know. Then again I also know that legal paper is 8.5x14 even though I have never had to use it.
Whenever someone questions what you know, the correct answer is “why don’t you?” - I will not be trivia-shamed!