## Monday, October 30, 2023

### Playful Math Carnival 169

Do you want to host the 13^2 Playful Math carnival in October? A month that had a Friday the 13th

Yes, please. Should have been on 10/13 instead of 10/31 but... apologies.

169 is a palindrome in two number bases less than 16. Which do you suppose?

All odd squares are centered octagonal numbers, but 169 is also a centered hexagonal. (Visualize more with Alex CHIK's GeoGebra.)

It is the smallest square that is prime upside down! What on earth could the next one be? Also 1666666999999999 is prime. What would you call that property? (Both via PrimeCurios.)

It's the last square in the Pell sequence, which are connected to approximations of π. What numerator n makes n/129 an approximation of π?
Puzzling

I'm using tangrams in an elementary math ed course as our primary manipulative to talk geometry, so I maybe have been too on the lookout. Simona Riva has a great GeoGebra collection of activities. Polypad has a great tangram puzzle collection. Here are some I found on a cereal box! But most of all, you have to see Paula Beardell Krieg's amazing series of tangram posts from this summer.

Futility Closet shared a ridiculous Lee Sallows pangeomagic square.

Bakingmoomins made a Hat Hat with the new Einstein tile.

Games

Always on the lookout for games. Tracy Proffitt has an awesome collection, well organized.

Interesting double or halve game from NRICH.

Sarah Carter shared the Ghost Game, fun logic/strategy game.

Sophia Wood and Kate Nowak with a great math game over on Brilliant: Halfsies

Content

Steve Phelps is the most amazing teacher with tech I know. He has a geometric constructions Desmos activity.

Eugenia Cheng on NPR addressing "Is math real?"

Mathigon now has an online implementation of Multiply by Heart by Dan Finkel.

NCTM has a new line of kids books on Powerful Mathematicians Who Changed the World.

Karen Campe has a calendar of problems every month, solutions at the end of the month. Here's October.

Humor

Sara VanDerWerf pointed out that SNL did a measurement skit. Warning: actually funny.

Kassia Wedekind shared a McSweeney's post from a teacher about teaching a curriculum with fidelity. Warning: a little too close to reality.

Fashion

Fashion? Libo Valencia has #mathplay t-shirts to go with his cool book.

Mathober

Sophia Wood started #Mathober a few years ago. Art and more on a math theme. Find many posts on Twitter or Mastodon or Bluesky. I've been liking Katie Steckles' π minute GeoGebra videos.

Last Stop

Last but not least, two playful bits from my students! Corinna, Leah, Jordan, Kacy and Jill made a Spooky Monster Escape Room in Desmos Activities. Ryan, Keri, Alex, Anna, and Emma have a new headbandz inspired math game for grades 5 and up called Math Heads. And by up, we mean up to college math majors!

At the home of the Playful Math Carnival, you can find previous, like 168 at find your factors, or connect to host yourself. I'd highly recommend it! Find the next one, Nov/Dec at the Fairy Math Mother. Should be magical.

This is my stop! Hope you had fun.

P.S. This will get you to go. Ed Southall asked AI to make images of people enjoying math...