Q: It has 20 congruent equilateral triangles as faces?

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An Icosahedron.

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Correct. Congruency means that two triangles have three pairs of congruent angles and corresponding sides of the same lengths. A pair of triangles with three pairs of congruent angles but sides of different lengths are similar, not congruent.

There are five regular polyhedra, also known as the Platonic solids. They are three-dimensional shapes where all of the faces are made up of the same regular polygon.They are:Tetrahedron with four faces (this one is like a pyramid, but with an equilateral triangle for the base and all of the faces)Cube with six faces (all squares)Octahedron with eight faces (all equilateral triangles)Dodecahedron with 12 faces (all regular pentagons)Icosahedron with 20 faces (all equilateral triangles)A square pyramid (like the Egyptian pyramids) is not a regular polyhedron, because it has two different types of regular polygons for faces.

According to some definitions an icosahedron is considered a Platonic solid so that each of its faces is an equilateral triangle. You would, therefore need three coplanar isosceles triangles to make each face of the icosahedron. Since there are 20 faces in an icosahedron, you would need 60 such triangles.

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An Icosahedron.

An icosahedron.

A solid with 8 faces is an octahedron.As all faces are the same it is a regular octahedron.As such it is one of the five platonic solids - the only five 3D objects that can be regular: the tetrahedron (4 equilateral triangles for the faces), the hexahedron (usually called a cube with 6 square faces), the octahedron (as asked, 8 equilateral triangles for the faces), dodecahedron (12 regular pentagons as faces), icosahedron (20 equilateral triangles as faces).

A regular icosahedron has 20 faces (equilateral triangles), 30 edges and 12 vertices.

1~Tetrahedron *4 faces (made of equilateral triangles) *6 edges *5 vertices 2~Hexahedron (cube) *6 faces (made of squares) *12 edges *8 vertices 3~Octrahedron *8 faces (made up of equilateral triangles) *12 edges *6 vertices 4~Icosahedron *20 faces (made of equilateral triangles) *30 edges *12 verticies 5~Dodecahedron *12 faces (made of pentagons) *30 edges *20 vertices.

It has 20 identical equilateral triangular faces.

A four sided figure would be a tetrahedron and a 20 sided would be an icosahedron. They both have equilateral triangles for faces so your question is a little incomplete.

Yes. The triangles have the same angle measures but different, similar side lengths. Think of two different sized equilateral triangles. One can have side lengths of 6 inches while the other has side lengths of 20 inches, but they still have congruent angles of 60 degrees. Each ratio of side lengths is equal [6/20=6/20=6/20].

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The polygons are the equilateral triangle, the square, and the regular pentagon. The faces of these platonic solids are made from the following polygons: tetrahedron - 4 triangles cube - 6 squares octahedron - 8 triangles dodecahedron - 12 pentagons icosahedron - 20 triangles

There are several: a tetrahedron with 4 equilateral triangles. An 8-sided solid (think of 2 Egyptian pyramids, turn one upside down and put the two square bases together). A 20-sided also has equilateral triangles.

Tetrahedron, Hexahedron(cube), Octahedron, Dodecahedron, and Icosahedron