Napkin Puzzle
From Samuel Loyd, in a book of puzzles. Nice write up about it at http://mindyourdecisions.com/blog/2014/03/24/monday-puzzle-three-napkins/, but spoiler alert: there's a solution.
"You are given three square napkins measuring 1 unit to a side. What’s the largest square table you can cover with the napkins? You cannot tear the napkins, but you can fold them or overlap them, and the napkins are allowed to drape over the side of the table."
I added the circular table because I was curious if they could cover more area that way or not. What do you think?