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Archive of posts filed under the Appreciation category.

Math at the Deli Counter

The deli counter at the grocery store sometimes offers a poignant glimpse into how the public engages with mathematics.

Whenever I order a fractional quantity of meat or cheese, I prepare myself to manage confusion. When a blank stare lingers at “three-quarters of a pound of ham”, I’ll follow up with “point seven five”. I’ve heard “One-third… What is that?” more than a few times. And a deli employee once asked me if I wanted my two-thirds of a pound of cheese in two bags. Usually my deli experiences go smoothly, but there are some employees with whom I know to skip fractions and immediately go to decimals.

None of this bothers me; if anything, it reminds me that fractions really are one of the first walls people hit when learning mathematics. And it increases my empathy for those who obviously weren’t helped enough when they first hit that wall, and still struggle to get over it as adults.

I’ve also witnessed math-shaming in this situation. “Yes. Point seven five. Three-quarters is 0.75. You don’t know what three-quarters is?” As rude as this behavior is, I can’t help but sympathize a little with the shamers themselves: what mathematical experiences have they had that makes them feel the need to use math to belittle others? Sadly, I think I know at least part of the answer to that question.

It’s important for those who of us who see math as a source of pleasure and power to remember that, for many, it can be a source of confusion and, sometimes, shame.

2017 — My Year in Math

Dan Meyer recently shared a fun and telling graph describing his year in math. Inspired by Dan’s idea, and by a Math for America workshop with data visualization innovator Mona Chalabi, I created my own Year in Math entry. Though the real inspiration, I guess, came from the world events that made me want to read more books and less internet.

You can find more takes on the Year in Math theme on Twitter.

I think this could make for a fun student project. I hope the students agree!

12/07/2017 — Happy Permutation Day!

Today we celebrate a Permutation Day! I call days like today permutation days because the digits of the day and the month can be rearranged to form the year.

Celebrate Permutation Day by mixing things up! Try doing things in a different order today. Just remember, for some operations, order definitely matters!

8/15/17 — Happy Pythagorean Triple Day!

Today we celebrate a rare Pythagorean Triple day!  And especially rare, as 8-15-17 is a primitive Pythagorean triple.  We won’t see many more of those!

Here’s an animation I made to celebrate.


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07/21/2017 — Happy Derangement Day!

Today we celebrate a Derangement Day!  Usually I call a day like today a Permutation Day because the digits of the day and month can be rearranged to form the year, but there’s something extra special about today’s date:

The numbers of the month and day are a derangement of the year:  that is, they are a permutation of the digits of the year in which no digit remains in its original place!

Derangements pop up in some interesting places, and are connected to many rich mathematical ideas.   The question “How many derangements of n objects are there?” is a fun and classic application of the principle of inclusion-exclusion.  Derangements also figure in to some calculations of e and rook polynomials.

So enjoy Derangement Day!  Today, it’s ok to be totally out of order.