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Dr. Shapiro's Puzzle of the Day

Today's Puzzle

Wednesday, December 16
It's the next-to-last puzzle of 2020!

These three animated GIFs all appear on the Wikipedia page for what invention?

   


     Note: Clicking "Submit" will send your response to Dr. Shapiro.

Yesterday's Puzzle + Solution

The Electoral College convened yesterday to formally elect the next President (spoiler alert: it's Joe Biden). In its reporting, the New York Times published a map representing each state as a block of squares, with 1 square per elector. Here are a few examples:
I happened to notice that four states on this map were shaped like Tetris pieces. Two of those were New Hampshire and Rhode Island. Can you identify the other two, shown below?

Bonus Question Which state was made up of 4 squares, but was NOT shaped like a Tetris piece?

Solution The L-shaped piece represents Idaho, the only one of the four Tetris states to have a distinctive enough shape to not just be a 2×2 square. (Delaware was an equally good guess based on shape, but Delaware has 3 electors and went blue.)

What about the square with mixed colors? Most states allot all their electors to the winner of the statewide vote. The two that don't are Nebraska and Maine. From the fact that Biden won most of the electors in this state, we can tell that it's Maine.

As for the bonus, every contiguous block of 4 unit squares is a Tetris piece. Which low-population state is (significantly) noncontiguous? That's Hawaii.

Here's the whole map, which I spent a long time staring at to figure out if the states fit together nicely. (They don't, and I'm mad about it.)

Someone should make a Tetris game where the pieces are states! You could play to gerrymander by disproportionately clearing rows of one color... oh man the election year brain worms have burrowed deeper than I thought. Help

Congratulations (with a pineapple for getting all 3 including the bonus) to yesterday's solvers Charlie🍍, Yana🍍, Maddy🍍, Graham, Kate🍍, and the Greggs🍍. Thanks to everybody who made a guess!

About This Site

Though he now teaches mathematics, Dr. (né Mr.) Shapiro's first job in a K–12 school was as a lunch monitor in Davis, CA. It was there that he originated the Puzzle of the Day, even rewarding correct answers with tickets in denominations like "15 points" (though without a clear idea of how he'd ultimately redeem these). Dr. Shapiro's favorite puzzle from this pre-professional era was "Tell me the location of the beehive on this campus."

Ten years later, Dr. Shapiro revived Puzzle of the Day at Proof School, writing each day's puzzle on a name tag. After 600 puzzles or so, he was just starting to feel normal about students reading his chest all the time when campus closed and the puzzle, like the rest of our lives, moved online. New puzzles are posted daily on school days.

Want to catch up on old PotDs? There's an archive currently containing puzzles from March to November 2020.