Faces, Face Area, and Vertices - SAT Subject Test in Math II

Card 0 of 9

Question

How many edges does a polyhedron with eight vertices and twelve faces have?

Answer

By Euler's Formula, the relationship between the number of vertices , the number of faces , and the number of edges of a polyhedron is

Set and and solve for :

The polyhedron has eighteen edges.

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Question

A regular tetrahedron has four congruent faces, each of which is an equilateral triangle.

The total surface area of a given regular tetrahedron is 600 square centimeters. To the nearest tenth of a centimeter, what is the length of each edge?

Answer

The total surface area of the tetrahedron is 600 square centimeters; since the tetrahedron comprises four congruent faces, each has area square centimeters.

The area of an equilateral triangle is given by the formula

Set and solve for :

centimeters.

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Question

A regular octahedron has eight congruent faces, each of which is an equilateral triangle.

The total surface area of a given regular octahedron is 400 square centimeters. To the nearest tenth of a centimeter, what is the length of each edge?

Answer

The total surface area of the octahedron is 400 square centimeters; since the octahedron comprises eight congruent faces, each has area square centimeters.

The area of an equilateral triangle is given by the formula

Set and solve for :

centimeters.

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Question

A regular icosahedron has twenty congruent faces, each of which is an equilateral triangle.

A given regular icosahedron has edges of length four inches. Give the total surface area of the icosahedron.

Answer

The area of an equilateral triangle is given by the formula

Since there are twenty equilateral triangles that comprise the surface of the icosahedron, the total surface area is

Substitute :

square inches.

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Question

How many edges does a polyhedron with fourteen vertices and five faces have?

Answer

By Euler's Formula, the relationship between the number of vertices , the number of faces , and the number of edges of a polyhedron is

.

Set and and solve for :

The polyhedron has seventeen edges.

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Question

How many faces does a polyhedron with nine vertices and sixteen edges have?

Answer

By Euler's Formula, the relationship between the number of vertices , the number of faces , and the number of edges of a polyhedron is

Set and and solve for :

The polyhedron has nine faces.

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Question

How many faces does a polyhedron with ten vertices and fifteen edges have?

Answer

By Euler's Formula, the relationship between the number of vertices , the number of faces , and the number of edges of a polyhedron is

Set and and solve for :

The polyhedron has seven faces.

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Question

How many faces does a polyhedron with ten vertices and sixteen edges have?

Answer

By Euler's Formula, the relationship between the number of vertices , the number of faces , and the number of edges of a polyhedron is

Set and and solve for :

The polyhedron has eight faces.

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Question

A convex polyhedron with eighteen faces and forty edges has how many vertices?

Answer

The number of vertices, edges, and faces of a convex polygon——are related by the Euler's formula:

Therefore, set and solve for :

The polyhedron has twenty-four faces.

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