My NRO monthly diaries close with a "Math Corner," usually set up as a brainteaser. I don't aim for anything heavy with these puzzles, just something for a person to while away ten minutes with during a coffee break.
Some of the puzzle solutions get a page of their own with my solution. If a puzzle didn't get a page of its own, that was because either (a) I thought it was too easy to be worth putting up a page for, or (b) I forgot. For cases covered by (a), there'll be an appropriate note in the following month's diary. For the (b) cases, I am sorry.