September 23, 2012

Geometry: Face, Vertices, and Edges (2nd Grade)

    We have been working on Faces, Vertices, and Edges of a solid figure. My son had some trouble with edges and how to find them. We found using 3D shapes and feeling the shape helped him identify the edges. We also used the following formula to make sure we answered the questions correctly. This formula also helps is your kids have problems picturing the 3D shapes in their heads. For my son seeing and feeling the shapes helps him find the edge. He can picture the shape and find the faces and vertices. I know hard to understand but that is how he works. 

  The formula is called the Euler's formula (see below for definition). 

Face + Vertices - Edge = 2     or     Vertices + Face - Edge = 2

     Since I do not know how to draw using blogger I have copied and pasted samples below from the site Math is Fun (http://www.mathsisfun.com/geometry/eulers-formula.html). I have been using this site to teach my son geometry, you should check them out. They also give you test question to answer after reading through the lesson. The best thing about this site is that it is FREE!!!


Name FacesVerticesEdgesF+V-E
Tetrahedron4462
Cube68122
Octahedron86122
Dodecahedron1220302
Icosahedron2012302

Euler's Formula: "Either of two important mathematical theorems of Leonhard Euler. The first is a topological invariance (see topology) relating the number of faces, vertices, and edges of any polyhedron." (http://www.merriam-webster.com/dictionary/euler's%20formula, 9/23/2012).

Polyhedron: a solid with flat faces (http://www.mathsisfun.com/geometry/polyhedron.html,9/23/2012)

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