**Math Concepts:** addition to thirty-one, thinking ahead.

**Players:** best for two.

**Equipment:** one deck of math cards.

### How to Play

Lay out the ace to six of each suit in a row, face up and not overlapping, one suit above another. You will have one column of four aces, a column of four twos, and so on—six columns in all.

The first player flips a card upside down and says its number value. Players alternate, each time turning down one card, mentally adding its value to the running total, and saying the new sum out loud. The player who exactly reaches thirty-one, or who forces the next player to go over that sum, wins the game.

### Variation

For a shorter game, use only the ace to four of each suit. Play to a target sum of twenty-two.

### History (and a Puzzle)

Thirty-One comes from British mathematician Henry Dudeney’s classic book, *The Canterbury Puzzles*. According to Dudeney, “This is a game that used to be (and may be to this day, for aught I know) a favourite means of swindling employed by card-sharpers at racecourses and in railway carriages.”

Dudeney challenges his readers to find a rule by which a player can always win: “Now, the question is, in order to win, should you turn down the first card, or courteously request your opponent to do so? And how should you conduct your play?”

Dudeney, H. E. *The Canterbury Puzzles,* Thomas Nelson and Sons, 1919 (originally published 1907); available at Project Gutenberg or the Internet Archive.

http://www.gutenberg.org/ebooks/27635

https://archive.org/details/canterburypuzzle00dudeuoft

This post is an excerpt from my book *Addition & Subtraction: Math Games for Elementary Students*, available now from your favorite online book dealer.

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