HSPT Math : Geometry

Study concepts, example questions & explanations for HSPT Math

varsity tutors app store varsity tutors android store

Example Questions

Example Question #4 : How To Find The Surface Area Of A Cylinder

What is the surface area of a cylinder with a radius of  and a height of ?

Possible Answers:

Correct answer:

Explanation:

When you're calculating the surface area of a cylinder, note that the cylinder will have two circles, one for the top and one for the bottom, and one rectangle that wraps around the "side" of the cylinder (it's helpful to picture peeling the label off a can of soup - it's curved when it's on the can, but really it's a rectangle that has been wrapped around).  You know the area of the circle formula; for the rectangle, note that the height is given to you but the width of the rectangle is one you have to intuit: it's the circumference of the circle, because the entire distance around the circle from one point around and back again is the horizontal distance that the area must cover.

Therefore the surface area of a cylinder = 

Example Question #1 : Solid Geometry

What is the surface area of a cube with a volume of 1728 in3?

Possible Answers:

1728 in2

432 in2

144 in2

864 in2

72 in2

Correct answer:

864 in2

Explanation:

This problem is relatively simple. We know that the volume of a cube is equal to s3, where s is the length of a given side of the cube. Therefore, to find our dimensions, we merely have to solve s3 = 1728. Taking the cubed root, we get s = 12.

Since the sides of a cube are all the same, the surface area of the cube is equal to 6 times the area of one face. For our dimensions, one face has an area of 12 * 12 or 144 in2. Therefore, the total surface area is 6 * 144 = 864 in2.

Example Question #13 : Solid Geometry

If the volume of a cube is 216 cubic units, then what is its surface area in square units?

Possible Answers:

108

216

36

54

64

Correct answer:

216

Explanation:

The volume of a cube is given by the formula V = s^{3}, where V is the volume, and s is the length of each side. We can set V to 216 and then solve for s.

\inline 216 = s^{3}

In order to find s, we can find the cube root of both sides of the equaton. Finding the cube root of a number is the same as raising that number to the one-third power.

\sqrt[3]{216}= 216^{1/3}=6=s

This means the length of the side of the cube is 6. We can use this information to find the surface area of the cube, which is equal to \inline 6s^{2}. The formula for surface area comes from the fact that each face of the cube has an area of s^2, and there are 6 faces in a cube.

surface area = 6s^{2}=6(6^{2})=6(36)=216

The surface area of the square is 216 square units.

The answer is 216.

Example Question #14 : Solid Geometry

You have a cube with sides of 4.5 inches. What is the surface area of the cube?

Possible Answers:

Correct answer:

Explanation:

The area of one side of the cube is:

A cube has 6 sides, so the total surface area of the cube is

Example Question #3 : How To Find The Surface Area Of A Cube

A cube has a surface area of 24. If we double the height of the cube, what is the volume of the new rectangular box?

Possible Answers:

Correct answer:

Explanation:

We have a cube with a surface area of 24, which means each side has an area of 4. Therefore, the length of each side is 2. If we double the height, the volume becomes .

Example Question #15 : Solid Geometry

A cube has a surface area of 10m2. If a cube's sides all double in length, what is the new surface area?

Possible Answers:

20m2

80m2

40m2

640m2

320m2

Correct answer:

40m2

Explanation:

The equation for surface area of the original cube is 6s2. If the sides all double in length the new equation is 6(2s)2 or 6 * 4s2. This makes the new surface area 4x that of the old. 4x10 = 40m2

Example Question #62 : Solid Geometry

A rectangular prism has a volume of 70 m3.  If the length, width, and height of the prism are integers measured in meters, which of the following is NOT a possible measure of the surface area of the prism measured in square meters?

Possible Answers:

118

280

174

178

214

Correct answer:

280

Explanation:

Since the volume is the product of length, width, and height, and each of these three dimensions are integers, it is important to know the factors of the volume.  70 = (2)(5)(7).  This implies that each of these factors (and only these factors with the exception of 1) will show up in the three dimensions exactly once.  This creates precisely the following five possibilities:

2, 5, 7

SA = 2((2)(5)+(2)(7)+(5)(7)) = 118

1, 7, 10

SA = 2((1)(7)+(1)(10)+(7)(10)) = 174

1, 5, 14

SA = 2((1)(5)+(1)(14)+(5)(14)) = 178

1, 2, 35

SA = 2((1)(2)+(1)(35)+(2)(35)) = 214

1, 1, 70

SA = 2((1)(1)+(1)(70)+(1)(70)) = 282

Example Question #5 : How To Find Surface Area

The three sides of a rectangular box all have integer unit lengths. If each of the side lengths is greater than one unit, and if the volume of the box is 182 cubic units, what is the surface area of the box in square units?

Possible Answers:

236

262

182

181

264

Correct answer:

262

Explanation:

Let's call the side lengths of the box l, w, and h. We are told that l, w, and h must all be integer lengths greater than one. We are also told that the volume of the box is 182 cubic units.

Since the volume of a rectangular box is the product of its side lengths, this means that lwh must equal 182. 

(l)(w)(h) = 182.

In order to determine possible values of l, w, and h, it would help us to figure out the factors of 182. We want to express 182 as a product of three integers each greater than 1. 

Let's factor 182. Because 182 is even, it is divisible by 2.

182 = 2(91).

91 is equal to the product of 7 and 13.

Thus, 182 = 2(7)(13).

This means that the lengths of the box must be 2, 7, and 13 units. 

In order to find the surface area, we can use the following formula:

surface area = 2lw + 2lh + 2hw.

surface area = 2(2)(7) + 2(2)(13) + 2(7)(13)

= 28 + 52 + 182

= 262 square units.

The answer is 262.

Example Question #11 : Prisms

A right rectangular prism has dimensions of 3 x 5 x 20. What is its surface area?

Possible Answers:

350

112

300

175

56

Correct answer:

350

Explanation:

There are six faces to a right, rectangular prism. Based on our dimensions, we know that we must have a face that is 3 x 5, a face that is 5 x 20 and a face that is 3 x 20. To think this through, imagine that the front face is 3 x 5, the right side is 5 x 20, and the top is 3 x 20. Now, each of these sides has a matching side opposite (the left has the right, the top has the bottom, the front has the back).

Therefore, we know we have the following areas for the faces of our prism:

2 * 3 * 5 = 30

2 * 5 * 20 = 200

2 * 3 * 20 = 120

Add these to get the total surface area:

30 + 200 + 120 = 350

Example Question #12 : Prisms

A right rectangular prism has dimensions of 12.4 x 2.3 x 33. What is its surface area?

Possible Answers:

470.58

941.16

513.62

1882.32

1027.24

Correct answer:

1027.24

Explanation:

There are six faces to a right, rectangular prism. Based on our dimensions, we know that we must have a face that is 12.4 x 2.3, a face that is 2.3 x 33 and a face that is 33 x 12.4. To think this through, imagine that the front face is 12.4 x 2.3, the left side is 2.3 x 33, and the top is 33 x 12.4. Now, each of these sides has a matching side opposite (the left has the right, the top has the bottom, the front has the back).

Therefore, we know we have the following areas for the faces of our prism:

2 * 12.4 * 2.3 = 57.04

2 * 2.3 * 33 = 151.8

2 * 12.4 * 33 = 818.4

Add these to get the total surface area:

57.04 + 151.8 + 818.4 = 1027.24

Learning Tools by Varsity Tutors