## Counting triangles on a tin ceiling (solution, take 2)

This is the solution to a problem I posed in my previous blog post. Please read that post first. [Update: I posted a solution to this problem two days ago. Yesterday Brent Yorgey pointed out that my analysis of “type 2” triangles was not quite correct. (See his comment below.) So I went back to…

## Counting triangles on a tin ceiling

This morning a student popped in to my office and said he had a math question for me, and that it wasn’t related to a class he was taking. He said that his apartment has a tin ceiling with square tiles. The tiles have X’s through them, as illustrated below: He asked: “Is there a…

## Kindergarten mathematics

This is a call for help. My son’s kindergarten teacher has invited parents to come in and talk about their careers. I’d like to go in and talk about math. I’d like to have some interactive hands-on mathematics activities for the kids to do. I also want them to be activities outside the typical kindergarten…