Today started our unit on solids. I started by doing Andrew Stadel’s File Cabinet 3-Act task. It was a great way to introduce the concept of concept area. I had students take 10 minutes to try to work out the answer and then had students talk with a random partner (had the students line up in order by the last two digits of their phone number and paired with the person next to them). After another 5 (really 10) minutes, those pairs had to give me one number that they thought was correct. I wrote all their guesses on the board and we talked through a couple of the class’s strategies. I gave another few minutes to let the pairs change some answers now that they’ve heard the discussion. Then, we watched the first part of the answer, until Mr. Stadel had finished one side. Once again, I gave a few minutes for the pairs to adjust any answers if needed. Then, we watched until he had finished four sides (the lateral area as we would come to define). The handles were a big focus point for the class – after seeing what he did with the handles, I gave students another few minutes to adjust their answers until we were ready for the big reveal. I now had 4 correct answers on the board and 4 others that were slightly off, but all were closer than what was given in the first round. The last post-it was great – students were excited to find out what it was and it gave a great tie-in to finding surface area.

Students then did a lot of practice in finding surface areas of prisms and pyramids. We get into surface area of spheres tomorrow, along with volume, and I’m hoping to be able to do Elissa Miller’s Tin Man Surface Area Project. I’m hoping to be able to get a few more cardboard objects before Monday, which is when I predict we will be able to start it. I’m so excited to try it!

Mes étudiants aiment bien le suspense d’une tâche mathématique.