High School Math : Cubes

Study concepts, example questions & explanations for High School Math

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Example Questions

Example Question #1 : How To Find The Surface Area Of A Cube

If the surface area of a cube equals 96, what is the length of one side of the cube?

Possible Answers:

6

3

5

4

Correct answer:

4

Explanation:

The surface area of a cube = 6a2 where a is the length of the side of each edge of the cube. Put another way, since all sides of a cube are equal, a is just the lenght of one side of a cube.

We have 96 = 6a→ a2 = 16, so that's the area of one face of the cube.

Solving we get √16, so a = 4

Example Question #1 : How To Find The Surface Area Of A Cube

What is the surface area of a cube with a side length of \displaystyle s=7.2in?

Possible Answers:

\displaystyle 331in^{2}

\displaystyle 311in^{2}

\displaystyle 373in^{2}

\displaystyle 52in^{2}

\displaystyle 86in^{2}

Correct answer:

\displaystyle 311in^{2}

Explanation:

In order to find the surface area of a cube, use the formula \displaystyle SA=6(s^{2}).

\displaystyle SA=6*(7.2in)^{2}

\displaystyle SA=6*51.84in^{2}

\displaystyle SA=311.04in^{2}

\displaystyle \rightarrow 311in^{2}

Example Question #34 : Solid Geometry

What is the surface area, in inches, of a rectangular prism with a length of , a width of \displaystyle w=18in, and a height of \displaystyle h=14in?

Possible Answers:

\displaystyle 2652.8in^{2}

\displaystyle 2319in^{2}

\displaystyle 2193.6in^{2}

\displaystyle 1108.8in^{2}

\displaystyle 6652.8in^{2}

Correct answer:

\displaystyle 2193.6in^{2}

Explanation:

In order to find the surface area of a rectangular prism, use the formula \displaystyle SA=(2*lw)+(2*wh)+(2*lh).

However, all units must be the same. All of the units of this problem are in inches with the exception of .

Convert to inches.

\displaystyle l=\frac{2.2ft}{1}*\frac{12in}{1ft}

\displaystyle l=26.4in

Now, we can insert the known values into the surface area formula in order to calulate the surface area of the rectangular prism.

\displaystyle SA=(2*26.4in*18in)+(2*18in*14in)+(2*26.4in*14in)

\displaystyle SA=(950.4in^{2})+(504in^{2})+(739.2in^{2})

\displaystyle SA=2193.6in^{2}

If you calculated the surface area to equal \displaystyle 6652.8in^{2}, then you utilized the volume formula of a rectangular prism, which is \displaystyle V=l*w*h; this is incorrect.

Example Question #2 : How To Find The Surface Area Of A Cube

Square_with_diagonalWhat is the surface area of a cube with a diagonal of ?

Possible Answers:

\displaystyle 84.05cm^{2}

\displaystyle 42.22cm^{2}

\displaystyle 59.22cm^{2}

\displaystyle 105.84cm^{2}

\displaystyle 52.92cm^{2}

Correct answer:

\displaystyle 52.92cm^{2}

Explanation:

A few facts need to be known to solve this problem. Observe that the diagonal of the square face of the cube cuts it into two right isosceles triangles; therefore, the length of a side of the square to its diagonal is the same as an isosceles right triangle's leg to its hypotenuse: \displaystyle 1:\sqrt{2}.

\displaystyle \frac{s}{d}=\frac{1}{\sqrt{2}}

Rearrange an solve for \displaystyle s.

Now, solve for the area of the cube using the formula .

\displaystyle SA=6*(\frac{4.2cm}{\sqrt{2}})^{2}

\displaystyle SA=\frac{6}{1}*(\frac{4.2cm}{\sqrt{2}}*\frac{4.2cm}{\sqrt{2}})

\displaystyle \rightarrow 52.92cm^{2}

Example Question #1 : How To Find The Surface Area Of A Cube

This figure is a cube with one face having an area of 16 in2.Cube

What is the surface area of the cube (in2)?

Possible Answers:

\displaystyle 96

\displaystyle 64

\displaystyle 256

\displaystyle 48

\displaystyle 16

Correct answer:

\displaystyle 96

Explanation:

The surface area of a cube is the sum of the area of each face.  Since there are 6 faces on a cube, the surface area of the entire cube is \displaystyle 6\cdot16.

Example Question #2 : How To Find The Surface Area Of A Cube

A cube has a height of 4 feet. What is the surface area of the cube in feet?

Possible Answers:

\displaystyle 96

\displaystyle 8

\displaystyle 80

\displaystyle 16

\displaystyle 64

Correct answer:

\displaystyle 96

Explanation:

To find the surface area of a cube, square the length of one edge and multiply the result by six: \displaystyle 6(a^{2})

\displaystyle 6(4^{2})=6(16)=96

Example Question #16 : Cubes

The side length of a particular cube is \displaystyle \frac{3}{2}. What is the surface area of this cube?

Possible Answers:

\displaystyle 18

\displaystyle \frac{27}{2}

\displaystyle 27

\displaystyle 9

\displaystyle \frac{9}{2}

Correct answer:

\displaystyle \frac{27}{2}

Explanation:

To find the surface of a cube, use the standard equation: 

\displaystyle SA=6a^2

where \displaystyle a denotes the side length.

Plug in the given value for \displaystyle a to find the answer:

\displaystyle SA=6\cdot \left(\frac{3}{2}\right)^2=6\cdot \left(\frac{9}{4}\right)=\frac{27}{2}

Example Question #17 : Cubes

Sarah is wrapping a birthday present.  The box is a cube with sides of \displaystyle 6\; in.  At a minimum, how many square feet of wrapping paper will she need?

Possible Answers:

\displaystyle 1.00\; ft^{2}

\displaystyle 1.50\; ft^{2}

\displaystyle 0.75\; ft^{2}

\displaystyle 1.25\; ft^{2}

\displaystyle 0.50\; ft^{2}

Correct answer:

\displaystyle 1.50\; ft^{2}

Explanation:

Remember, \displaystyle 6\; in=0.50\; ft.

For a cube:

\displaystyle SA = 6s^{2}

Thus \displaystyle 6(0.50)^{2}=6(0.25)=1.50\; ft^{2}.

Example Question #11 : Cubes

Possible Answers:

\displaystyle p^{2}

\displaystyle 12p

 

\displaystyle 6p^{2}

\displaystyle 4p^{2}

\displaystyle p^{3}

Correct answer:

\displaystyle 6p^{2}

Explanation:

Example Question #42 : Solid Geometry

Find the surface area of the following cube:

Length_of_diagonal

Possible Answers:

\displaystyle 80\ m^2

\displaystyle 88\ m^2

\displaystyle 90\ m^2

\displaystyle 96\ m^2

 

\displaystyle 82\ m^2

Correct answer:

\displaystyle 96\ m^2

 

Explanation:

The formula for the surface area of a cube is

\displaystyle SA=6(s)^2,

where \displaystyle s is the length of the side.

Plugging in our values, we get:

\displaystyle SA=6(4\ m)^2

\displaystyle SA=96\ m^2

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