How to find the surface area of a cube

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SAT Math › How to find the surface area of a cube

Questions 1 - 10
1

A certain cube has a side length of 25 m. How many square tiles, each with an area of 5 m2, are needed to fully cover the surface of the cube?

100

200

500

750

1000

Explanation

A cube with a side length of 25m has a surface area of:

25m * 25m * 6 = 3,750 m2

(The surface area of a cube is equal to the area of one face of the cube multiplied by 6 sides. In other words, if the side of a cube is s, then the surface area of the cube is 6_s_2.)

Each square tile has an area of 5 m2.

Therefore, the total number of square tiles needed to fully cover the surface of the cube is:

3,750m2/5m2 = 750

Note: the volume of a cube with side length s is equal to _s_3. Therefore, if asked how many mini-cubes with side length n are needed to fill the original cube, the answer would be:

s3/n3

2

Find the surface area of a cube given side length of 3.

Explanation

To find the surface area of a cube means to find the area around the entire object. In the case of a cube, we will need to find that area of all the sides and the top and bottom. Since a cube has equal side lengths, the area of each side and the area of the top and bottom will all be the same.

Recall that the area for a side of a cube is:

From here there are two approaches one can take.

Approach one:

Add all the areas together.

Approach two:

Use the formula for the surface area of a cube,

In this particular case we are given the side length is 3.

Thus we can find the surface area to be,

by approach one,

and by appraoch two,

.

3

Find the surface area of a cube with side length 2.

Explanation

To solve, simply use the formula for the surface area of a cube. Thus,

4

The surface areas of six cubes form an arithmetic sequence. The two smallest cubes have sidelengths 10 and 12, respectively. Give the surface area of the largest cube.

Explanation

The surface area of a cube can be calculated by squaring the sidelength and multiplying by six. The two smallest cubes therefore have surface areas

and

The surface areas form an arithmetic sequence with these two surface areas as the first two terms, so their common difference is

.

The surface area of the largest, or sixth-smallest, cube, is

5

You own a Rubik's cube with a volume of . What is the surface area of the cube?

Not enough information to solve

Explanation

You own a Rubik's cube with a volume of . What is the surface area of the cube?

To solve for edge length, think of the volume of a cube formula:

Now, we have the volume, so just rearrange it to solve for side length:

Next, recall the surface area of a cube formula:

Plug in and simplify to get:

6

What is the surface area of a cube with a side length of 30?

Explanation

Write the formula for the surface area of a cube.

Substitute the side.

7

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

1728 in2

432 in2

72 in2

144 in2

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.

8

Find the surface area of a cube with side length 8.

Explanation

To solve, simply use the formula for the surface area of a cube.

If this is not a formula you have committed to memory, remember that a cube has 6 faces with equal area. So, start by calculating the surface area of one side (64) and add it 6 times. Thus,

9

A company wants to build a cubical room around a cone so that the cone's height and diameter are 3 inch less than the dimensions of the cube. If the volume of the cone is 486π ft3, what is the surface area of the cube?

69,984 in2

726 in2

513.375 in2

486 in2

73,926 in2

Explanation

To begin, we need to solve for the dimensions of the cone.

The basic form for the volume of a cone is: V = (1/3)πr_2_h

Using our data, we know that h = 2r because the height of the cone matches its diameter (based on the prompt).

486_π_ = (1/3)πr_2 * 2_r = (2/3)_πr_3

Multiply both sides by (3/2_π_): 729 = _r_3

Take the cube root of both sides: r = 9

Note that this is in feet. The answers are in square inches. Therefore, convert your units to inches: 9 * 12 = 108, then add 3 inches to this: 108 + 3 = 111 inches.

The surface area of the cube is defined by: A = 6 * _s_2, or for our data, A = 6 * 1112 = 73,926 in2

10

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

Explanation

The area of one side of the cube is:

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

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