Intermediate Geometry : Solid Geometry

Study concepts, example questions & explanations for Intermediate Geometry

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Example Questions

Example Question #59 : Cylinders

A cylinder is cut in half and placed on top of a rectangular prism as shown by the figure below.

12

Find the volume of the figure.

Possible Answers:

Correct answer:

Explanation:

13

In order to find the volume of the figure, we will first need to find the volumes of the rectangular prism and the half cylinder.

From the figure, you should notice that the length of the prism is also the diameter of the half cylinder. Thus, half the length of the prism will also be the radius of the half cylinder. Also, notice that the width of the prism will be the height of the cylinder.

For the given cylinder then, find the radius.

Then, recall how to find the volume of a cylinder:

, where  is the radius and  is the height.

Divide the volume by  to find the volume of the half cylinder.

Next, recall how to find the volume of a rectangular prism.

Plug in the given values to find the volume of the rectangular prism.

To find the volume of the figure, add the volume of the half cylinder and the volume of the rectangular prism together.

Remember to round to  places after the decimal.

Example Question #60 : Cylinders

Inscribed

The above diagram shows a sphere inscribed inside a cylinder.

The sphere has a volume of 100. Give the volume of the cylinder.

Possible Answers:

Correct answer:

Explanation:

Let  be the radius of the sphere. Then the radius of the base of the cylinder is also , and the height of the cylinder is .

The volume of the cylinder is

,

which, after substituting, is

The volume of the sphere is 

Therefore, the ratio of the former to the latter is

and 

That is, the volume of the cylinder is  times that of the sphere, so the volume of the cylinder is

.

 

Example Question #61 : Cylinders

During a snow storm,  of snow was collected. If the snow were put in a circular lot that had a radius of , how high would the snow on the lot be?

Possible Answers:

Correct answer:

Explanation:

Since we are putting the snow on a circular base, we are dealing with a cylinder. Notice that the radius of the cylinder and the volume of the cylinder are already given to you.

Recall how to find the volume of a cylinder:

Rearrange the equation to solve for the height:

Plug in the given volume and radius:

The height is between  and  meter.

Example Question #1 : How To Find The Length Of An Edge Of A Prism

The volume of a prism is  .

Given the length is  and the height is , find the width of the prism.

Possible Answers:

Correct answer:

Explanation:

The volume of a prism is length times width times height.

We are given the length is 7m and the width is 5m.

So, we plug these into our formula:

 .

We then solve for height:

 .

The height is therefore 6m. 

Example Question #1 : How To Find The Length Of An Edge Of A Prism

Find the missing edge of the prism when its volume is .

Find_the_edge

Possible Answers:

Correct answer:

Explanation:

The goal is to find the height of the rectangular prism with the given information of its width and length. The volume of a rectangular prism is , where  is width and  is height. 

Because we're given the final volume and two of the three variables, we can substitute in the information we know and solve for the missing variable. 

Therefore, the height of the prism is .

Example Question #1 : How To Find The Length Of An Edge Of A Prism

A rectangular prism has a volume of  cubic meters. Its length is twice its width, and its height is twice its length. What is the length of the prism?

Possible Answers:

Correct answer:

Explanation:

If we let  be the width of our prism, then since the length is twice the width, our length would be .  Since the height is twice the length, our height would be .

Since the volume of a rectangular prism is simply the product of width, length, and height, we get

We then simply solve for the width.

Therefore, our width is 3.  Since our length is twice the width, the length is 6.

Example Question #2 : How To Find The Length Of An Edge Of A Prism

A right, rectangular prism has a volume of  cubic inches. Its width is  inches and its height is  inches. What is its length?

Possible Answers:

None of the other answers.

Correct answer:

Explanation:

The formula for the volume of a right, rectangular prism is , so substitute the known values and solve for lenght.  

.  So the length is 8 inches.

Example Question #1 : How To Find The Length Of An Edge Of A Prism

The surface area of a right rectangular prism is  square cm. Its length is  cm and its height is  cm. Find the width of the prism.

Possible Answers:

None of the other answers.

 

Correct answer:

 

Explanation:

Use the formula for finding the surface area of a right, rectangular prism,

and substitute the known values, and then solve for w.

So, 

So, the width is 7 cm.

Example Question #2 : How To Find The Length Of An Edge Of A Prism

The height of a retangular prism is three times its width; its length is twice its width. Its surface area is 1,078 square inches. Give the width of the box.

Possible Answers:

Correct answer:

Explanation:

Since the length of the box is twice the width and the height is three times the width,  and 

The surface area of the box is

To find the width:

Example Question #1 : Prisms

Find the surface area of the rectangular prism:

 The_surface_area_of_a_prism

Possible Answers:

Correct answer:

Explanation:

The_surface_area_of_a_prism

To find the surface area of a prism, the problem can be approached in one of two ways.

1. Through an equation that uses lateral area
2. Through finding the area of each side and taking the sum of all the faces

Using the second method, it's helpful to realize rectangular prisms contain  faces. With that, it's helpful to understand that there are  pairs of sides. That is, there are two faces with the same dimensions. Therefore, we really only have three sides for which we need to calculate areas: 

Faces 1 & 2:



Faces 3 & 4:

Faces 5 & 6:

Now, we can add up the areas of all six sides:

The surface area is .

 

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