1. Space and Shape Unit
Grade 9 Math

2. Platonic solids
E4 Make and apply generalizations about the properties of platonic solids

3. To prepare for this lesson
What is a polygon?
What are some polygons you know?
What is a regular polygon?
To prepare for this lesson

4. Platonic solids activity #1
In our class we have 2 platonic solids
We are going to begin the lesson by making platonic solids
We will then try and find what is the same about all of them
Platonic solids activity #1

5. Activity #1 Each person will cut out and assemble a 3 D platonic solid
You will work in groups of 5 to compare the 5 different solids that have been made
When your group has the 5 solids made go to the next slide and start to answer the questions
Activity #1

6. Activity #1 Complete the table to the right with your group
There are 5 platonic solids:
Tetrahedron: Has 4 faces
Hexahedron: Has 6 faces
Octahedron: Has 8 faces
Dodecahedron: Has 10 faces
Icosahedron: Has 20 faces 1 2 3 4 5
Number of faces
Number of vertices
Number of edges
Number of sides meeting at a vertex
Activity #1

7. When constructing a platonic solid, what is a rule for the sides of the regular polyhedra?
Why are there only 5 platonic solids/regular polyhedral?
What can you say about vertices in a specific regular polyhedral? Across the platonic solids?
Watch this video for both comedic and visualization purposes: gFtho
Answers:
Activity #1

8. Duality activity #2 Some platonic solids have duality
After watching the video, try to create a definition of duality with your group
What shapes have dulaity?
In your groups, use sketches of 2D and 3D tetrahedrons to show that it is it’s own dual or not
Duality activity #2