Plane shapes such as squares, circles and triangles are known as flat surfaces. They can be drawn on paper with a pencil or marker.
As a teacher, you might have heard that cones and cylinders don’t have faces or edges. But what does that mean?
Ask students to think about this question. Lead them with a think-pair-share exercise using a 3D shape (for example, a rectangular prism).
Show students that a face is a flat surface of a solid object. Explain that a cube has six faces and a sphere has one curved surface.
Demonstrate how the number of faces and the surface area are related to each other by holding a rectangular prism and counting the number of faces that you see on each side. You might use stickers or sticky notes to temporarily mark the faces as you count them so that all students can see it.
Generally, the total surface area of a cylinder is found by adding the area of its curved surface and two circular bases. The curved surface area is then multiplied by the base radius and the height of the cylinder to find the height of the cylinder.
