Grade school geometry introduces students to the number of sides found on basic 3D shapes. Distribute worksheets that each have basic but various net images and ask students to color each shape within the net a different color. Have the students cut along the outside of the net shape. Collect students' nets and show the class how the individual shapes within the net form a hollow 3D figure keeping the colorful sides on the exterior. Count the sides with the class and tell them the name of the particular shape.
Dissecting a 3D object activity works well as an introductory lesson for geometric nets for grade school and middle school students because it breaks down the concept of geometric nets visually. Ask each student to bring an empty toilet paper roll to class, which represents a 3D model. Instruct the students to cover the cylinder, including the holes at each end, neatly without crinkled edges and overlaps using a single sheet of paper. The activity objective is to get students to cut the length of the toilet paper cylinder so it lays flat, trace around the flattened rectangle-shaped cylinder and draw two circles attached to the long sides of the rectangle.
Assist seventh, eighth or ninth grade geometry classes with determining geometric net possibilities of a cube. Separate the class into groups of three to four students. Distribute graph paper and inform students that a 3D cube is made up of of six equal squares. Ask groups to develop as many nets for a cube as possible in approximately 30 minutes. Tell the class that they can cut out their nets to determine if they form cubes. Share the nets created by each group and determine if all 11 possibilities are reached.
Polyhedra is another name for a 3D shape that has flat sides that are joined at the edges. Polyhedras can have many flat sides making this in-class activity suitable for advanced geometry classes. Ask each student to develop three nets with more than six flat surfaces. Students will work by themselves for the first 30 minutes and then have the opportunity to form small groups for the next 30 minutes. Some students may find that they created similar 3D objects to group members, but once groups form, students cannot copy a group member's shape.