Anytime you can have food in class it’s a good day (unless you are the custodian sweeping up popcorn. I’m sorry!) I came up with this project probably four years ago. We did the whole pour the water from a cone into a cylinder thing, and it was ok, but I wanted something better. While eating popcorn at the movies, my daughter and I started talking about the cost of the popcorn and the sizes available. Putting those two ideas together, this project was born.
The first year I had students create a cylinder and then figure out how to make a cone with the same base area and height. This was a struggle and I ended up showing them. It does involve a lot of thinking and many would not have gotten there on their own. The following year, I created a hand-drawn example of how to calculate the dimensions of the cone. I now have the information in Google Slides for students to use.
There are great discussions about the slant height becoming the radius of the cone. I do have to show students a visual of this and they are always amazed. Once they see the visual and we discuss how the circumference of the cone piece has to meet up with the base circle, they begin to see how it all fits together.
I’ve included the activity for the first day. I’ve popped trashbags full of popcorn and I’ve popped microwave popcorn. If you can get your concession stand to open up their popcorn machine then you have it made.
As a follow-up activity, I decided to have students calculate the cost and the amount for which they could sell their popcorn. This allows them to make some decisions about which container would be best. Many of them tell me that it doesn’t matter which one is the best deal because the cone of popcorn would be inconvenient. š
Popcorn Surface Area & Volume Follow-up activity
Enjoy!
Infinitely Teaching 
I really like this activity. I would love to use it but I am struggling on how to get back to the central angle number in your presentation. Any help would be appreciated