There are a few of us who like to do Puzzle/Math contests. But I would say for us and the people who participate its not really about the prize but about the challenge. Most of the people who participate tell me this. The issue we have is getting the pieces seen.
https://steemit.com/contest/@nicnas/usdusdusd-free-steem-dollars-puzzle-contest-2-usdusdusd
@mathworksheets will do them after teaching a lesson on a certain subject as well.