Gr 7–8 · 50 min
Cylinders and cones
Coming soon. We're checking this lesson against the app, step by step, so it works when you run it with a class. You can read the plan now. The lesson pack, teaching mode and assigning open once it's checked.
Build a cylinder and a cone with the same radius and height: the cone holds a third.
Ontario Gr 7–8 · Spatial Sense E2 (cones are enrichment) · Common Core 8.G.C.9
Learning goals
- Use the formulas for the volumes of cylinders and cones
- Find the surface area of a cylinder from its net
Plan
- 1
Build both15 minStudents
Build the cylinder without a top (cut the top circle off the net), and a cone with radius 3 and height 8 (open the Cone from this lesson's page: it has the same sizes and prints at real size too).
- 2
Fill10 minStudents
Fill the cone with rice and pour it into the cylinder. How many cones fill the cylinder?
- 3
Formulas15 minStudents
Cylinder: π r² h. Cone: ⅓ π r² h. Work out both with π = 3.14 and compare with FoldNets' readout. It uses a more exact π, so the last digit can differ.
- 4
Unroll10 minStudents
The cylinder's side unrolls into a rectangle 2πr long. Find the surface area from the net.
To talk about
- Why is the side of a cylinder's net a rectangle?
- What shape is a cone's side on the net?