Content code
m1673
Slug (identifier)
eulers-theorem
Grades
Grade 5
Grade 6
Equivalent file in the opposite grade group
Topic
Mathematics
Content
Title (level 2)
5th and 6th Grade
Title slug (identifier)
fifth-and-sixth-grade
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Contenu
Title
What is Euler’s Theorem?
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Euler's theorem was discovered in the 18th century by the mathematician Leonhard Euler. It is a formula that helps calculate the relationships between the number of faces, vertices, and edges of a convex polyhedron. The missing term can be found when two of the three terms present in Euler's formula are known.

To learn more about faces, vertices, and edges, read the concept sheet Faces, Edges, and Vertices.

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Here are three formulas that allow you to apply Euler’s theorem. The results are the same when you use any of these formulas.

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Three Formulas to Apply Euler’s Theorem
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Determining the number of edges of a polyhedron using the formula F + V - 2 = E
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Corps

To determine the number of edges of a convex polyhedron using the formula |F + V - 2 = E,| I have to follow these steps.

  1. I write Euler's theorem by replacing |F| with the number of faces and |V| with the number of vertices of the convex polyhedron.

  2. I add the number of faces and the number of vertices. Then, I rewrite the equation.

  3. I subtract |2| from the sum obtained in step 2.

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Corps

How many edges does a convex polyhedron with |8| faces and |12| vertices have?

  1. I write Euler's theorem by replacing |F| with the number of faces and |V| with the number of vertices of the convex polyhedron.

    I replace |F| with |8|, because the polyhedron has |8| faces.

    I replace |V| with |12,| because the polyhedron has |12| vertices.

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  1. I add the number of faces and the number of vertices. Then, I rewrite the equation.

    |8+12=20|

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  1. I subtract |2| from the sum obtained in step 2.

    |20-2=18|

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A convex polyhedron with |8| faces and |12| vertices has |18| edges.

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How to find the number of edges of a polyhedron using the formula F + V - E = 2
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Corps

To determine the number of edges of a convex polyhedron using the formula |F + V - E = 2,| I have to follow these steps.

  1. I write Euler's theorem by replacing |F| with the number of faces and |V| with the number of vertices of the convex polyhedron.

  2. I add the number of faces and the number of vertices. Then, I rewrite the equation.

  3. I find the missing term (|E|) in the subtraction.

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Corps

How many edges does a convex polyhedron with |7| faces and |10| vertices have?

  1. I write Euler's theorem by replacing |F| with the number of faces and |V| with the number of vertices of the convex polyhedron.

    I replace |F| with |7,| because the polyhedron has |7| faces.

    I replace |V| with |10,| because the polyhedron has |10| vertices.

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  1. I add the number of faces and the number of vertices. Then, I rewrite the equation.

    |7+10=17|

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  1. I find the missing term (|E|) in the subtraction.

    To review how to find a missing term, read the concept sheet Finding a missing term in a subtraction.

    |17-2=15|

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A convex polyhedron with |7| faces and |10| vertices has |15| edges.

Title
How to find the number of edges of a polyhedron using the formula F + V = E + 2
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Content
Corps

To determine the number of edges of a convex polyhedron using the formula |F + V = E + 2,| I have to follow these steps.

  1. I write Euler's theorem by replacing |F| with the number of faces and |V| by the number of vertices of the convex polyhedron.

  2. I add the number of faces and the number of vertices. Then, I rewrite the equation.

  3. I find the missing term (|E|) in the addition.

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Corps

How many edges does a convex polyhedron with |10| faces and |16| vertices have?

  1. I write Euler's theorem by replacing |F| with the number of faces and |V| with the number of vertices of the convex polyhedron.

    I replace |F| with |10,| because the polyhedron has |10| faces.

    I replace |V| with |16,| because the polyhedron has |16| vertices.

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  1. I add the number of faces and the number of vertices. Then, I rewrite the equation.

    |10+16=26|

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  1. I find the missing term (|E|) in the addition.

    To review how to find a missing term, read the concept sheet Finding a Missing Term in an Addition.



    |26-2=24|

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A convex polyhedron with |10| faces and |16| vertices has |24| edges.

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Corps

Using this formula, you can also find the number of faces and vertices of a polyhedron.

To find the number of faces, you need to know the number of vertices and edges.

Example:

How many faces does a polyhedron with |6| vertices and |9| edges have?

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Example of applying the formula F + V = E + 2 to find the number of faces.
Corps

To find the number of vertices, you need to know the number of faces and edges.

Example:

How many vertices does a polyhedron with |5| faces and |9| edges have?

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Example of applying the formula F + V = E + 2 to find the number of vertices.
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