SAT II Math II : 3-Dimensional Geometry

Study concepts, example questions & explanations for SAT II Math II

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Example Questions

Example Question #2 :Faces, Face Area, And Vertices

Aregular octahedronhas 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?

Possible Answers:

Correct answer:

Explanation:

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

The area of an equilateral triangle is given by the formula

Setand solve for:

centimeters.

Example Question #3 :Faces, Face Area, And Vertices

Aregular icosahedronhas 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.

Possible Answers:

Correct answer:

Explanation:

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.

Example Question #4 :Faces, Face Area, And Vertices

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

Possible Answers:

Correct answer:

Explanation:

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

Setandand solve for:

The polyhedron has nine faces.

Example Question #5 :Faces, Face Area, And Vertices

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

Possible Answers:

Insufficient information is given to answer the question.

Correct answer:

Explanation:

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

Setandand solve for:

The polyhedron has eighteen edges.

Example Question #6 :Faces, Face Area, And Vertices

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

Possible Answers:

Insufficient information is given to answer the question.

Correct answer:

Explanation:

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

Setandand solve for:

The polyhedron has seven faces.

Example Question #7 :Faces, Face Area, And Vertices

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

Possible Answers:

Correct answer:

Explanation:

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

Setandand solve for:

The polyhedron has eight faces.

Example Question #8 :Faces, Face Area, And Vertices

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

Possible Answers:

Correct answer:

Explanation:

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

Therefore, setand solve for:

The polyhedron has twenty-four faces.

Example Question #9 :Faces, Face Area, And Vertices

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

Possible Answers:

Correct answer:

Explanation:

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

.

Setandand solve for:

The polyhedron has seventeen edges.

Example Question #1 :3 Dimensional Axes And Coordinates

Which of the following numbers comes closest to the length of line segment in three-dimensional coordinate space whose endpoints are the origin and the point?

Possible Answers:

Correct answer:

Explanation:

Use the three-dimensional version of the distance formula:

The closest of the five choices is 7.

Example Question #2 :3 Dimensional Axes And Coordinates

A line segmentin three-dimensional space has midpoint;has midpoint.

has Cartesian coordinates;has Cartesian coordinates. Give the-coordinate of.

Possible Answers:

Correct answer:

Explanation:

The midpoint formula for the-coordinate

将应用两次,一次找到吗-coordinate of, then again to find that of.

First, set, the-coordinate of, and, the-coordinate of, and solve for, the-coordinate of:

Now, set, the-coordinate of, and, the-coordinate of, and solve for, the-coordinate of:

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