Icosahedron

A Maths Starter of The Day

How Many Triangles?

 

 

 

 

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  • Mike Litoris, Mianus, Nebraska
  • Wednesday, March 04, 2009
  • "Any DnD (Dungeons & Dragons) player will immediately recognize this familiar shape as a d20. A good task is to ask the students to form the net, or better yet, make there own."

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This starter has scored a mean of 3.6 out of 5 based on 127 votes.
 

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Answer
20
(or 40 if you count the reflection)

As the title suggests, the shape is a regular icosahedron, one of the five Platonic solids. It is a polyhedron composed of 20 triangular faces, with five meeting at each of the 12 vertices connected by 30 edges.

Can you sketch a net for this shape?

Have you seen the Great Dodacahedron?

Other shape counting starters:

How Many Squares 1? | How Many Squares 2?
How Many Triangles 1? | How Many Triangles 2? | How Many Triangles 3?
How Many Rectangles? | Rectangles Investigation | Icosahedron

The animation at the top of this page was adapted from one created by Ramandeep Singh and made available on www.Flashkit.com