Today was day 2 of our discussion of circumference of a circle and that mysterious number Pi. After trying to teach this topic for 15 years, I think I have finally found an approach that my students remember.

This is how Friday began

Yes, that is me hula hooping in class. I read about this idea at (http://www.loledservices.com/). I began the lesson by discussing with my students about how athletically challenged I was and told them I really needed to decide which hula hoop, large or small, was going to be the easiest one to use. After discussing their ideas with their table, one person from each table related to the class the teams ideas. The students decided that I would not have to move as fast to make the larger hoop spin since it was bigger around on the outside so the larger hoop would be the best bet for me. Then the hula hooping commenced and the laughter ensued.

Then I had the students form teams of 2 or 3 and grab their own hula hoop. After a bit of wild hula hooping, students sat down and determined how many bottle caps it would take to go around the outside of the hula hoop. The students also calculated how many bottle caps it took to go all the way across the hula hoop through the center of the circle.

Students returned to their seats and posted their teams information on the board. As a class, we estimated that the circumference was about three times the diameter. During this discussion is also when we decided we needed better names for “that distance around the hula hoop” and “that distance across the hula hoop through the center” and I introduced the vocabulary circumference and diameter.

We investigated this idea by going into the hallway and making human circles. I would say a diameter number of people and then the students would determine how many people it would take to go around that diameter.