*Math Teachers at Play* is a traveling collection of math tidbits — games, lesson ideas, and more — from around the Internet. It moves around from month to month, and the September edition is now posted at *1001 Math Problems* blog. What a fun list of math posts to browse!

Welcome to the 78th edition of the Math Teachers At Play math education blog carnival, which I am thrilled to be hosting this month in celebration of my soon-to-be-released book, Camp Logic. What is the blog carnival? It is a monthly snapshot of some interesting recent ideas and activities posted by math education bloggers all over the internet.

By tradition, I begin with a fun fact about the number 78:

Seventy-eight is the 12th triangle number, which means that it is the sum of the integers from 1 to 12. Therefore, it is also the total number of gifts given on the last day in the song “The Twelve Days of Christmas!” …