The Third Millennium of Those “Find My Age” Algebra Problems

I’d explain the title of this post, but you already know what I’m talking about. I refer to questions like this one, from the 4th century:

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I, for one, pity old Demochares—enumerating the fractions of his life, yet unable to recall his own age. It’s a bizarre, selective senility, like something from an Oliver Sacks book: “The Man Who Mistook His Life for a Math Problem.”

Or consider this problem, from the 21st century:

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Over the last three millennia, much has changed. Civilizations have risen, collided, and fallen. Revolutions have left legacies in blood and ink. There have been, for good and for ill, 417 million Marvel films. Yet somehow, these age-based math puzzles have remained a constant.

What’s the case for them? Continue reading


The ABC Book of e

Roughly speaking, e is 2.718.

More precisely, e is the essence of existence, the fount of human joy, and (for folks who worry that Pi Day is kinda played out) the perfect constant around which to build your mathematical festivities (e-clairs, anyone?).

Get excited, citizens of math, because Wednesday, February 7th, 2018 is e Day: 2/7/18.

(Well… in America, anyway. Our international pals may wait until Monday, July 2nd.)

In honor of this noble number, I offer an alphabetical celebration:

Continue reading

The Twitter Logo is Just Circles

a roundup post that I wrote in November and never shared,
and now I’ve kinda stopped doing roundup posts,
but hey, here ya go

Suterisms: I recently came across the work of cartoonist David Suter. His images are hard to describe. Artful cartoons? Cartoonish art? Visual puns? More like visual wordplay; “thoughtplay?” It’s what you’d get if you hired MC Escher as a political cartoonist. This one was a favorite of mine:

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Belatedly: RIP, Voevodsky: A tribute to the visionary mathematician Vladimir Voevodsky, who died in 2017.

Continue reading

A Borrowed Joke (and 15 other math cartoons)

The Fence Post Error

2017.12.1 fencepost problem

I drew this one at the request of Prof. Jim Propp, who writes the excellent Mathematical Enchantments and whose November essay Impaled on a Fencepost explored the kind of off-by-one errors that I make at least 17 times per day. (Or is it 18?)

Greetings from Heisenberg!

2017.12.4 postcard from heisenberg

Tourist bureau of Würzburg, Germany: please feel free to sell these. Continue reading

Things to Know About the Year 2018

Whatever your grievances against 2016 as a year, it was a stellar number. Like a picnic with milkshakes and beer, this integer was fun for the whole family.

Just look at these equations:

1 new year

After this crowd-pleaser came 2017, a prime year, which engendered this brilliant Tweet from Matt Parker:

That brings us to 2018.

It’s not triangular, like 2016.

It’s not prime, like 2017.

Is it, then, worthless?

Well, I myself am neither triangular nor prime. But if the roles were reversed, I like to think 2018 would do its best to uncover my special qualities and catalogue them in a blog post. So I went to do “research” (my codeword for “Google searches”).

What secret mathematical properties and pleasures will our new year contain? Continue reading

The Terrible Truth About Dreidel

From time to time, a journalist may face a soul-shattering dilemma. A scoop so shocking it cannot be withheld, yet so terrible it cannot be told.

And what goes for journalists, goes double for stick-figure cartooning math teachers. Thus, as one who loves truth even at its ugliest, I choose to divulge a fact sure to rattle your faith in humanity itself:

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The game of dreidel is built on a lie. Continue reading