# Archive | Puzzles

## Double Check, Where the Moved Piece Is Not One of the Checking Pieces

An interesting thing happened yesterday in a game between my son and my father: a double check, in which the moved piece was not one of the checking pieces. (In a usual double check, a piece moves, placing the king in check but also discovering a check by another piece. To quote a formulation on the U.S. Chess Federation Site, “Double check is a more dangerous form of a discovered check where not only the hidden piece attacks the king, but also the piece that moves.”) How did this happen? Everyone was following the normal rules of chess.

Note that a move that promotes a pawn, thus creating a check from the promoted piece and a discovered check because of the pawn move, would not qualify as an answer, since the moved piece (albeit not the same one that started the move) is one of the checking pieces. [...]

## Alpha, Bravo, Charlie, David

Usually the words used to represent letters are “alpha, bravo, charlie, delta, …” but in one instance (that I know of) it’s “alpha, bravo, charlie, david, ….” What is it, and why? [...]

## Earwigging

Several related Mississippi legal rules prohibit “earwigging.” Without looking it up, can you tell what it means?

Note that no other states even mention “earwig” or its forms in their statutes, even though there’s nothing Mississippi-specific about that behavior. Also, only six cases accessible in Westlaw mention the term (setting aside those mentioning either insects or people with that name), all from Mississippi.

Thanks to Bill Raftery (Gavel to Gavel) for the pointer. [...]

## Etymological Oxymorons

“Splitting the atom,” it turns out, is what one might call an etymological oxymoron — “atom” comes from the Greek “a-,” meaning “not,” and “tomos,” meaning cut. The atom was that which couldn’t be split, at least through chemical processes, but it turns out that it can be split through nuclear processes (whether generated by humans or stemming from natural radioactivity).

Likewise with “gym clothes,” since “gymnasium” comes from the Greek verb meaning “to train in the nude.” And “jumbo shrimp” indeed qualifies, since shrimp seems to come from an Old English term meaning “to shrink.”

What other examples are there? Please note them in the comments, and quote the relevant etymology from some credible source (preferably a dictionary). [...]

## Math Puzzle

Consider the product 1! x 2! x 3! x … x 99! x 100! — a very big number, but that doesn’t faze us mathematicians (since you won’t need to multiply out in any event).

The puzzle: Can you, by omitting exactly one of the factorials from the product, produce a perfect square? (For instance, omitting 3! would make the product be 1! x 2! x 4! x 5! x … x 99! x 100!.) [...]

## Heads of Executive Departments (E.g., Treasury, State, Etc.)

The heads of executive departments have many powers and many duties. But what are the powers and duties that the Constitution expressly assigns to them? [...]

## China

China is a country. China is a kind of dish. According to dictionary.com, “china” is also “a playing marble of china, or sometimes of porcelain or glass.” But it turns out that, in some states, a term pronounced — but not spelled — “china” is a bit of legalese. What does it mean? [...]

## Puzzle

You and I have 12 pennies, arranged in a row, heads up.

We take turns. On each turn, the player can flip either (A) one coin or (B) two coins that are adjacent to each other. The player can choose on his turn which of these do, and which coin or coins to flip.

Once a coin has been flipped, it can’t be flipped again.

(Example: I start by flipping coin 5. Now it’s your turn; you can then, for instance, flip coin 12, or coins 9 and 10, or coins 3 and 4. But you can’t reflip coin 5, and you can’t flip coins 4 and 6, because they aren’t adjacent.)

The goal is to be the one to flip the last coin or coins, leaving the coins all tails.

What’s the winning strategy, and who’s the winner — the person who goes first, or the person who goes second? [...]

## Reporter Series

Lawyers know that the Federal Reporter, which started out just as “F.,” is now on “F.3d.” The Northeastern Reporter is “N.E.3d.” Which reporters have a series number that’s higher than 3d? [...]

## 10,640

This number can be seen, if you’re imaginative, as representing a particular online work (or set of works, if you prefer to view it that way). Which one? [UPDATE: Please explain your answer.] [...]

## Fun Math Puzzle

Pretty easy, but I found it amusing. Treating “^” as meaning exponentiation, and treating the exponentiation chain as going on infinitely, solve for x:

x^(x^(x^(x^(x^(x^…))))) = 2

## Astronomical Vegetable

What vegetable’s name is etymologically connected — distantly, to be sure — to an astronomical concept (not just the name of a particular object, such as the name of a planet or a star)? There might well be many answers, but I have one in mind. [...]

## Cryptarithms

Cool math puzzles, which I remember from my childhood (though the ones I did were in Russian). The principle is that you must solve a puzzle such as OLD+OLD+OLD = GOOD or COUPLE+COUPLE = QUARTET, where each letter stands for a digit and no two letters standing for the same digit. A fun project for kids who like math, and maybe even for adults. Thanks to my colleague Doug Lichtman for the pointer. [...]

## Puzzle

Here’s an easy one: White Russia, Yellow China, Black Turkey, Red ___. [...]

## Math Puzzle

My friend Haym Hirsh passes along this problem: Prove that every positive integer has a multiple (other than 0) that consists only of zeros and ones. (Thus, for instance, one such multiple for 6 is 1110.) [...]