I Love Weird Stuff Like This

Shuffle a deck of cards and start dealing them face up one at a time into a pile, counting down from 10 as you go β€” that is, say β€œ10” as you deal the first card, β€œ9” as you deal the second, and so on. As soon as you say a number that matches the value of the card you’re dealing, stop dealing and start a new pile. Face cards count as 10. If you count down to 1 without finding a match, β€œkill” the pile by putting a card face down on top of it. Repeat this procedure until you’ve dealt four piles. (If all four piles are β€œkilled,” which is very unlikely, shuffle the whole deck and start over.) When the four piles are finished, add the values of the cards at the top of each β€œliving” pile. Call that sum k. Now deal k cards from the remainder of the deck, and then count the cards that remain. There will always be eight.

(Martin Gardner, β€œCurious Counts,” Math Horizons 10:3 [February 2003], 20-22.) via the good folks at Futility Closet.

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