Advanced Geometry : Cones

Study concepts, example questions & explanations for Advanced Geometry

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Example Questions

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Example Question #31 : How To Find The Surface Area Of A Cone

In the figure below, a cone is placed on top of a cylinder so that they share the same base. Find the surface area of the figure.

12

Possible Answers:

Correct answer:

Explanation:

13

First, find the lateral surface area of the cone.

Plug in the given slant height and radius.

Next, find the surface area of the cylinder:

The surface area of the cylinder is the sum of the lateral surface area of the cylinder and its two bases. However, since one base of the cylinder is covered up by the cone, we will need to subtract that area out of the total surface area of the cylinder.

Plug in the given height and radius to find the surface area of the cylindrical portion of the figure:

To find the surface area of the figure, add together the lateral area of the cone with the surface area of the cylindrical portion of the figure.

Make sure to round to  places after the decimal.

Example Question #31 : How To Find The Surface Area Of A Cone

In the figure below, a cone is placed on top of a cylinder so that they share the same base. Find the surface area of the figure.

11

Possible Answers:

Correct answer:

Explanation:

13

First, find the lateral surface area of the cone.

Plug in the given slant height and radius.

Next, find the surface area of the cylinder:

The surface area of the cylinder is the sum of the lateral surface area of the cylinder and its two bases. However, since one base of the cylinder is covered up by the cone, we will need to subtract that area out of the total surface area of the cylinder.

Plug in the given height and radius to find the surface area of the cylindrical portion of the figure:

To find the surface area of the figure, add together the lateral area of the cone with the surface area of the cylindrical portion of the figure.

Make sure to round to  places after the decimal.

Example Question #31 : How To Find The Surface Area Of A Cone

In the figure below, a cone is placed on top of a cylinder so that they share the same base. Find the surface area of the figure.

10

Possible Answers:

Correct answer:

Explanation:

13

First, find the lateral surface area of the cone.

Plug in the given slant height and radius.

Next, find the surface area of the cylinder:

The surface area of the cylinder is the sum of the lateral surface area of the cylinder and its two bases. However, since one base of the cylinder is covered up by the cone, we will need to subtract that area out of the total surface area of the cylinder.

Plug in the given height and radius to find the surface area of the cylindrical portion of the figure:

To find the surface area of the figure, add together the lateral area of the cone with the surface area of the cylindrical portion of the figure.

Make sure to round to  places after the decimal.

Example Question #31 : Solid Geometry

In the figure below, a cone is placed on top of a cylinder so that they share the same base. Find the surface area of the figure.

8

Possible Answers:

Correct answer:

Explanation:

13

First, find the lateral surface area of the cone.

Plug in the given slant height and radius.

Next, find the surface area of the cylinder:

The surface area of the cylinder is the sum of the lateral surface area of the cylinder and its two bases. However, since one base of the cylinder is covered up by the cone, we will need to subtract that area out of the total surface area of the cylinder.

Plug in the given height and radius to find the surface area of the cylindrical portion of the figure:

To find the surface area of the figure, add together the lateral area of the cone with the surface area of the cylindrical portion of the figure.

Make sure to round to  places after the decimal.

Example Question #31 : How To Find The Surface Area Of A Cone

Cone

Figure NOT drawn to scale.

The base of the above cone has circumference 50. Give the surface area of the cone. 

Round to the nearest whole number.

Possible Answers:

Correct answer:

Explanation:

The surface area of a cone can be calculated using the formula

where  is the radius of the base and  is the slant height. The slant height is known to be 20.

The radius of the circular base can be found by dividing its circumference 50 by :

 

Set  and , and evaluate:

Example Question #32 : How To Find The Surface Area Of A Cone

Cone

Figure NOT drawn to scale.

The base of the above cone has area 50. Give the surface area of the cone. 

Round to the nearest whole number.

Possible Answers:

Correct answer:

Explanation:

The area  and the radius  of the circular base are related by the formula

The area of the circle is 50, so set , then solve for :

Divide by :

Take the square root of both sides:

The surface area of the cone is the sum of the areas of the base and the lateral area. The lateral area of the cone can be found from the radius  and the slant height  using the formula

Set  and :

Add the area of the base, 50:

Example Question #31 : Solid Geometry

Cone

Figure NOT drawn to scale.

The base of the above cone has area 50. Give the surface area of the cone. 

Round to the nearest whole number.

Possible Answers:

Correct answer:

Explanation:

The area  and the radius  of the circular base are related by the formula

The area of the circle is 50, so set , then solve for :

Divide by :

Take the square root of both sides:

Now examine the figure below.

Cone

The slant height can be calculated from the height  and the radius  by way of the Pythagorean Theorem:

The surface area of the cone is the sum of the areas of the base and the lateral area. The lateral area of the cone can be found from the radius  and the slant height  using the formula

Set  and :

Add the area of the base, 50, to this lateral area to obtain the surface area:

.

Example Question #33 : How To Find The Surface Area Of A Cone

Cone

Figure NOT drawn to scale.

The base of the above cone has circumference 50. Give the surface area of the cone. 

Round to the nearest whole number.

Possible Answers:

Correct answer:

Explanation:

The surface area of a cone can be calculated using the formula

where  is the radius of the base and  is the slant height. 

The radius of the circular base can be found by dividing its circumference 50 by :

 

Examine the figure below. 

Cone

The slant height can be calculated from the height  and the radius  by way of the Pythagorean Theorem:

Set  and  in the surface area formula:

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