## Sunday, October 25, 2015

### Math Teachers at Play, #91

Number 91 feels like we're closing in on 100. The last time I hosted MT@P, we were at #71 and I managed to include 71 posts. I wasn't quite that ambitious this time. (Old math posts don't go stale. You might enjoy browsing through a bunch of the old Math Teachers at Play blog carnivals. And don't forget our partner carnival: the Carnival of Mathematics.)

If there are 14 people in a group, and each shakes hands with each other, there will be 91 handshakes. (Can you see why?)

91 = 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 + 11 + 12 + 13
(which makes it triangular)

and

91 = 7 * 13
(the middle and last numbers in the sum above)

Will this always happen for triangular numbers?

### Games & Puzzles

• Shannon Duncan, a 6th grade math & science teacher, shares 4 Reasons to Promote Math Success through Games at the MIND Research Institute blog, illustrating her ideas with some of the games she has her students playing. I especially like the first point - making a mind-body connection.
• John Golden (@mathhombre) shares Angle of Coincidence at his blog, Math Hombre, about an angle identification game he's developing. Ask your students to playtest it and give him feedback! John also wrote about the start of the semester, and included a game called In or Out?  that looks fun.
• Jeff Trevaskis shares a Multiplication Tic-Tac-Toe Game at his blog, webmath.
• Carole Fullerton shares Number Tile Puzzles at  her blog, Mathematical Thinking.
• Gray Antonick interviewed Paul Salomon in the New York Times Numberplay column, about his Imbalance Puzzles, one of many puzzles and games featured in Playing with Math: Stories from Math Circles, Homeschoolers, and Passionate Teachers (my book, published in April!).

### Geometry

• Stephen Cavadino (@srcav) shares Parallelograms at his blog, cavmaths, on a student's creative way to find the area of a parallelogram.
• Ioana I Pantiru (@LThMathematics) shares Playing with Paper Folding at her blog, Life Through a Mathematician's Eyes, showing the steps of an origami construction. In her post, Maths Class Everywhere, she asks readers to take her survey of math classes around the world.
• Curmudgeon shares Circles on a Lattice, at their blog, Math Arguments 180. I wonder if this would make a good problem for a math circle...
• Greg Blonder, a professor of manufacturing and product design, shares Trisecting the Angle With a Straightedge, at Plus Maths.
• There have been lots of posts in the past few months about classifications of pentagons (here's one), because a new (15th) type of pentagon that will tile the plane was recently found. Here's a good background post, from before the discovery, from the Mathematical Tourist.

### Ideas for Learning ...

• Kate Snow (@katesmathhelp) shares How to Teach Your Kids to Read Math  at her blog, Kate's Homeschool Math Help. I'm still trying to teach my college students how to read math, with some of the same tips.
• Manan (@shalock) shares Becoming Mathematically Fluent at his blog, Math Misery.
• Shecky (@sheckyr) shares True Deep Beauty ... at his blog, Math-Frolic, about the how our understanding of math deepens.
• Chris Rime is making monthly math calendars (Algebra I, II, and Geometry), available as doc or pdf at his blog, Partially Derivative.

### ... And Teaching

• Tom Bennison (@DrBennison) shares How to enjoy your NQT Year at his blog, Mathematics and Coding. [I had to look up NQT. It means newly qualified teacher, and in England and Wales, you are "inducted" in your NQT year, (generally) your first year of paid teaching.] I like his suggestion to make time for doing some math(s) yourself.

### Announcements

I'm going to the Joint Mathematics Meetings in January in Seattle. I'd love to connect with other bloggers who are going. There's a math poetry reading plus art exhibit on Thursday evening at 5:30. You can get all the details from JoAnne Growney's Intersections blog.