SAT II Math I : Geometry

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

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Example Questions

Example Question #12 : Cones

What is the surface area of a cone with a radius of 6 in and a height of 8 in?

Possible Answers:

36π in2

60π in2

66π in2

112π in2

96π in2

Correct answer:

96π in2

Explanation:

Find the slant height of the cone using the Pythagorean theorem:  r2 + h2 = s2 resulting in 62 + 82 = s2 leading to s2 = 100 or s = 10 in

SA = πrs + πr2 = π(6)(10) + π(6)2 = 60π + 36π = 96π in2

60π in2 is the area of the cone without the base.

36π in2 is the area of the base only.

Example Question #1 : How To Find The Surface Area Of A Cone

Use the following formula to answer the question.

The slant height of a right circular cone is . The radius is , and the height is . Determine the surface area of the cone. 

Possible Answers:

 

Correct answer:

 

Explanation:

Notice that the height of the cone is not needed to answer this question and is simply extraneous information. We are told that the radius is , and the slant height is

First plug these numbers into the equation provided.

Then simplify by combining like terms.

Example Question #11 : Surface Area

The slant height of a cone is ; the diameter of its base is one-fifth its slant height. Give the surface area of the cone in terms of .

Possible Answers:

Correct answer:

Explanation:

The formula for the surface area of a cone with base of radius  and slant height  is

.

The diameter of the base is ; the radius is half this, so 

Substitute in the surface area formula:

Example Question #1 : How To Find The Surface Area Of A Cone

The radius of the base of a cone is ; its slant height is two-thirds of the diameter of that base. Give its surface area in terms of .

Possible Answers:

Correct answer:

Explanation:

The formula for the surface area of a cone with base of radius  and slant height  is

.

The diameter of the base is twice radius , or , and its slant height is two-thirds of this diameter, which is . Substitute this for  in the formula:

Example Question #2 : How To Find The Surface Area Of A Cone

The radius of the base of a cone is ; its height is twice of the diameter of that base. Give its surface area in terms of .

Possible Answers:

Correct answer:

Explanation:

The formula for the surface area of a cone with base of radius  and slant height  is

.

The base has radius  and diameter . The height is twice the diamter, which is . Its slant height can be calculated using the Pythagorean Theorem:

Substitute  for  in the surface area formula:

Example Question #122 : Geometry

The height of a cone is ; the diameter of its base is twice the height. Give its surface area in terms of .

Possible Answers:

Correct answer:

Explanation:

The formula for the surface area of a cone with base of radius  and slant height  is

.

The diameter of the base is twice the height, which is ; the radius is half this, which is .

The slant height can be calculated using the Pythagorean Theorem:

Substitute  for  and  for  in the surface area formula:

Example Question #123 : Geometry

The circumference of the base of a cone is 80; the slant height of the cone is equal to twice the diameter of the base. Give the surface area of the cone (nearest whole number).

Possible Answers:

Correct answer:

Explanation:

The formula for the surface area of a cone with base of radius  and slant height  is

.

The slant height is twice the diameter, or, equivalently, four times the radius, so

and

The radius of the base is the circumference divided by , which is 

 

Substitute:

Example Question #2 : How To Find The Surface Area Of A Cone

The circumference of the base of a cone is 100; the height of the cone is equal to the diameter of the base. Give the surface area of the cone (nearest whole number).

Possible Answers:

Correct answer:

Explanation:

The formula for the surface area of a cone with base of radius  and slant height  is

.

The diameter of the base is the circumference divided by , which is 

This is also the height .

The radius is half this, or 

The slant height can be found by way of the Pythagorean Theorem:

Substitute in the surface area formula:

Example Question #21 : Surface Area

If a cone were unfurled into a 2-dimensional figure. The lateral area of the cone would look most like which figure? 

Possible Answers:

Circle

Triangle

Rectangle

Sector of a Circle

Correct answer:

Sector of a Circle

Explanation:

When creating a net image of a 3D figure - one imagines it is made of paper and is unfurled into its' 2D form. The lateral portion of the cone cone would be unfurled into the image of a Sector of a Circle. To include the full surface area of the cone a circle is included to form the base of the cone as in the figure below. The lateral area portion is the top part of the figure below. 

Cone net

Example Question #121 : Geometry

Find the surface area of a cube with side length of 6in.

Possible Answers:

Correct answer:

Explanation:

A cube is made up of 6 identical sides. Find the area of one side and multiplying it by 6 will result in the surface area of a cube.

a is the side length, in this case 6in.

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