This is the centennial year of much beloved Martin Gardner’s birth. In honor of this great puzzlemeister and mathematics popularizer, the theme for this year’s Math Awareness Month is “*Mathematics, Magic, and Mystery*.”

What is your favorite mathematical puzzle?

I’d love to hear it—and will collect the results in a subsequent post in April.

*Hint:* knock on any math prof’s door and ask to borrow a Gardner book (they’re sure to have one), or spend some time perusing old Scientific American issues in the Cudahy Stacks.

**Update.*** Another “Hint”:* A new puzzle is being revealed each day on the Math Aware website. Which is your favorite?

April 1. magic squares

April 2. braids

April 3. fibonacci cards

April 4. quick: what’s the square of 347?

April 5. mind reading

April 7. hexaflexagons

April 8. geometric vanish (a la S.Loyd)

April 9. number tricks

April 10. more card tricks

April 11. (un)knots

April 12. ??