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Dr. Shapiro's Puzzle of the Day

Today's Puzzle

Thursday, February 25
Regular readers of Puzzle of the Day have already learned that when I want to type ¯\_(ツ)_/¯, I just Google "shrug", then copy and paste from the results—with the side effect of seeing this guy each time.

Recently I used a similar tactic to get the Unicode characters for a certain math operation. Instead, I ended up with a lot of results like the image at left. Which operation was I searching for?

   


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Yesterday's Puzzle + Solution

Water towers hold a lot of water. You might even think that holding water is their purpose, their raison d'être.

But why store water in a tower? What other purpose does that serve that, say, an underground tank wouldn't?

BONUS PUZZLE: I've never been to Italy, but I have seen the glorious water tower at left in person. (It's in Florence, Kentucky.)

This water tower originally had a slightly different phrase painted on it, which had to be changed because it ran afoul of advertising laws. The city opted for the cheapest fix they could. What place of business did the water tower originally advertise?

Solution Isn't it amazing that you turn a faucet and get running water instantaneously? This miracle depends on pressurization. It's slow work to pump water upward, but once you have water up high, gravity will happily carry it down the pipes quickly on demand and pressurize it on the way. That's what water towers accomplish. (Skyscrapers, being generally taller than water towers, need their own pumps and tanks.)

One way to look at water towers is that they store energy as well as water. Leo told me: "With an efficiency of roughly 75%, this is used across the world as a form of energy storage. You can reverse the polarity of the DC generators in a hydroelectric dam during periods of lower usage, and then use the extra water during peak usage. I know all this because Switzerland uses a lot of hydropower and first used it for grid storage."

BONUS: The tower originally said FLORENCE MALL. Wikipedia has the full story. Honorable mention to Peter for his guess of FLORISTS Y'ALL.

Congratulations to yesterday's winners Ena, Alex Z., Leo S., Peter M., Josh M., Connor, Jacob C., Atticus, 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 December 2020.