SAT Math : Solid Geometry

Study concepts, example questions & explanations for SAT Math

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Example Questions

Example Question #11 : Prisms

The dimensions of a right rectangular prism are such that the second dimension is twice the length of the first and the third is twice the length of the second. If the volume of the prism is 216 cubic units, what is its surface area?

Possible Answers:

126 square units

189 square units

215 square units

None of the other answers

252 square units

Correct answer:

252 square units

Explanation:

Based on our prompt, we can say that the prism has dimensions that can be represented as:

Dim1: x

Dim2: 2 * Dim1 = 2x

Dim3: 2 * Dim2 = 2 * 2x = 4x

More directly stated, therefore, our dimensions are: x, 2x, and 4x. Therefore, the volume is x * 2x * 4x = 216, which simplifies to 8x3 = 216 or x3 = 27. Solving for x, we find x = 3. Therefore, our dimensions are:

x = 3

2x = 6

4x = 12

Or: 3 x 6 x 12

Now, to find the surface area, we must consider that this means that our prism has sides of the following dimensions: 3 x 6, 6 x 12, and 3 x 12. Since each side has a "matching" side opposite it, we know that we have the following values for the areas of the faces:

2 * 3 * 6 = 36

2 * 6 * 12 = 144

2 * 3 * 12 = 72

The total surface area therefore equals: 36 + 144 + 72 = 252 square units.

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

The area of a given object is 30,096 in2. What is the area of this object in ft2?

Possible Answers:

None of the other answers

209 ft2

2508 ft2

1254 ft2

1881 ft2

Correct answer:

209 ft2

Explanation:

Converting squared units is not difficult, though you have to be careful not to make a simple mistake. It is tempting to think you can merely divide the initial value (30,096) by 12, as though you were converting from inches to feet.

Begin by thinking this through as follows. In the case of a single dimension, we know that:

1 ft = 12 in   or   1 in = (1/12) ft

Now, think the case of a square with dimensions 1 ft x 1 ft. This square has the following dimensions in inches: 12 in x 12 in. The area is therefore 12 * 12 = 144 in2. This holds for all two-dimensional conversions. Therefore, the two dimensional conversion equation is:

1 ft2 = 144 in2   or   1 in2 = (1/144) ft2

Based on this, we can convert our value 30,096 in2 thus: 30,096/144 = 209 ft2.

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

The area of a given object is 24 yd2. What is the area of this object in in2?

Possible Answers:

20,736 in2

None of the other answers

10,368 in2

31,104 in2

864 in2

Correct answer:

31,104 in2

Explanation:

Converting squared units is not difficult, though you have to be careful not to make a simple mistake. It is tempting to think you can merely multiply the initial value (24) by 36, as though you were converting from yards to inches.

Begin by thinking this through as follows. In the case of a single dimension, we know that:

1 yd = 36 in

Now, think the case of a square with dimensions 1 yd x 1 yd. This square has the following dimensions in inches: 36 in x 36 in. The area is therefore 36 * 36 = 1296 in2. This holds for all two-dimensional conversions. Therefore, the two dimensional conversion equation is:

1 yd2 = 1296 in2

Based on this, we can convert our value 24 yd2 thus: 24 * 1296 = 31,104 in2.

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

Angie is painting a 2 foot cube for a play she is in. She needs 25\hspace{1 mm}mL of paint for every square foot she paints. How much paint does she need?

Possible Answers:

600\hspace{1 mm}mL

It is impossible to convert between metric units and feet.

None of the available answers

1.041\overline{6}\hspace{1 mm}mL

100\hspace{1 mm}mL

Correct answer:

600\hspace{1 mm}mL

Explanation:

First we must calculate the surface area of the cube. We know that there are six surfaces and each surface has the same area:

Area=6(2^2)=6\times 4=24\hspace{1 mm}feet^2

Now we will determine the amount of paint needed

24\hspace{1 mm}feet^2\times \frac{25\hspace{1 mm}mL}{1\hspace{1 mm}foot^2}=600\hspace{1 mm}mL

Example Question #84 : Solid Geometry

What is the surface area of an equilateral triangluar prism with edges of 6 in and a height of 12 in? 

Let  and .

Possible Answers:

Correct answer:

Explanation:

The surface area of the prism can be broken into three rectangular sides and two equilateral triangular bases.

The area of the sides is given by:  , so for all three sides we get .

The equilateral triangle is also an equiangular triangle by definition, so the base has congruent sides of 6 in and three angles of 60 degrees.  We use a special right traingle to figure out the height of the triangle: 30 - 60 - 90.  The height is the side opposite the 60 degree angle, so it becomes 3\sqrt{3} or 5.196. 

The area for a triangle is given by  and since we need two of them we get .

Therefore the total surface area is .

Example Question #21 : Prisms

Box

The shaded face of the above rectangular prism is a square. In terms of , give the surface area of the prism.

Possible Answers:

Correct answer:

Explanation:

Since the front face of the prism is a square, the common sidelength - and the missing dimension - is .

There are two faces (front and back) that are squares of sidelength ; the area of each is the square of this, or .

There are four faces (left, right, top, bottom) that are rectangles of dimensions 25 and ; the area of each is the product of the two, .

The surface area is the total of their areas:

 

Example Question #71 : Solid Geometry

Box 3

The shaded face of the above rectangular prism is a square. In terms of , give the surface area of the prism.

Possible Answers:

Correct answer:

Explanation:

Since the top face of the prism is a square, the common sidelength - and the missing dimension - is 25.

The surface area  of a rectangular prism with length , width , and height  can be found using the formula

.

Setting, and solving for :

Example Question #245 : Geometry

A rectangular box has a length of 2 meters, a width of 0.5 meters, and a height of 3.2 meters. How many cubes with a volume of one cubic centimeter could fit into this rectangular box?

Possible Answers:

3.2 x 102

3.2 x 10-3

3.2

3,2 x 103

3.2 x 106

Correct answer:

3.2 x 106

Explanation:

In order to figure out how many cubic centimeters can fit into the box, we need to figure out the volume of the box in terms of cubic centimeters. However, the measurements of the box are given in meters. Therefore, we need to convert these measurements to centimeters and then determine the volume of the box.

There are 100 centimeters in one meter. This means that in order to convert from meters to centimeters, we must multiply by 100.

The length of the box is 2 meters, which is equal to 2 x 100, or 200, centimeters.

The width of the box is 0.5(100) = 50 centimeters.

The height of the box is 3.2(100) = 320 centimeters.

Now that all of our measurements are in centimeters, we can calculate the volume of the box in cubic centimeters. Remember that the volume of a rectangular box (or prism) is equal to the product of the length, width, and height.

V = length x width x height

V = (200 cm)(50 cm)(320 cm) = 3,200,000 cm3

To rewrite this in scientific notation, we must move the decimal six places to the left.

V = 3.2 x 106 cm3

The answer is 3.2 x 106.

Example Question #2 : Prisms

A rectangular prism has a length that is twice as long as its width, and a width that is twice as long as its height. If the surface area of the prism is 252 square units, what is the volume, in cubic units, of the prism?

Possible Answers:

432

1728

27

216

108

Correct answer:

216

Explanation:

Let l be the length, w be the width, and h be the height of the prism. We are told that the length is twice the width, and that the width is twice the height. We can set up the following two equations:

l = 2w

w = 2h

Next, we are told that the surface area is equal to 252 square units. Using the formula for the surface area of the rectangular prism, we can write the following equation:

surface area = 2lw + 2lh + 2wh = 252

We now have three equations and three unknowns. In order to solve for one of the variables, let's try to write w and l in terms of h. We know that w = 2h. Because l = 2w, we can write l as follows:

l = 2w = 2(2h) = 4h

Now, let's substitute w = 2h and l = 4h into the equation we wrote for surface area.

2(4h)(2h) + 2(4h)(h) + 2(2h)(h) = 252

Simplify each term.

16h2 + 8h2 + 4h2 = 252

Combine h2 terms.

28h2 = 252

Divide both sides by 28.

h2 = 9

Take the square root of both sides.

h = 3.

This means that h = 3. Because w = 2h, the width must be 6. And because l = 2w, the length must be 12.

Because we now know the length, width, and height, we can find the volume of the prism, which is what the question ultimately requires us to find.

volume of a prism = l • w • h

volume = 12(6)(3)

= 216 cubic units

The answer is 216.

Example Question #1 : Finding Volume Of A Rectangular Prism

The dimensions of Treasure Chest A are 39” x 18”. The dimensions of Treasure Chest B are  16” x 45”. Both are 11” high. Which of the following statements is correct?

Possible Answers:

There is insufficient data to make a comparison between Treasure Chest A and Treasure Chest B.

Treasure Chest A has the same surface area as Treasure Chest B.

Treasure Chest B can hold more treasure.

Treasure Chest A can hold more treasure.

Treasure Chest A and B can hold the same amount of treasure.

Correct answer:

Treasure Chest B can hold more treasure.

Explanation:

The volume of B is 7920 in3. The volume of A is 7722 in3. Treasure Chest B can hold more treasure.

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