High School Math : How to find the length of an edge of a cube

Study concepts, example questions & explanations for High School Math

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Example Questions

Example Question #1 : Cubes

Our backyard pool holds 10,000 gallons.  Its average depth is 4 feet deep and it is 10 feet long.  If there are 7.48 gallons in a cubic foot, how wide is the pool? 

Possible Answers:

100 ft  

30 ft  

 33  ft   

133 ft  

7.48 ft  

Correct answer:

 33  ft   

Explanation:

There are 7.48 gallons in cubic foot. Set up a ratio:

1 ft3 / 7.48 gallons = x cubic feet / 10,000 gallons

Pool Volume = 10,000 gallons = 10,000 gallons * (1 ft3/ 7.48 gallons) = 1336.9 ft3

Pool Volume = 4ft x 10 ft x WIDTH = 1336.9 cubic feet

Solve for WIDTH:

4 ft x 10 ft x WIDTH = 1336.9 cubic feet

WIDTH = 1336.9 / (4 x 10) = 33.4 ft

Example Question #1 : Cubes

A cube has a volume of 64cm3. What is the area of one side of the cube?

Possible Answers:

16cm

4cm2

16cm2

4cm

16cm3

Correct answer:

16cm2

Explanation:

The cube has a volume of 64cm3, making the length of one edge 4cm (4 * 4 * 4 = 64).

So the area of one side is 4 * 4 = 16cm2

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

Given that the suface area of a cube is 72, find the length of one of its sides. 

Possible Answers:

\(\displaystyle \sqrt{6}\)

\(\displaystyle 2\sqrt{3}\)

\(\displaystyle 3\)

\(\displaystyle 6\)

\(\displaystyle 3\sqrt{2}\)

Correct answer:

\(\displaystyle 2\sqrt{3}\)

Explanation:

The standard equation for surface area is 

\(\displaystyle SA=6a^2\)

where \(\displaystyle a\) denotes side length. Rearrange the equation in terms of \(\displaystyle a\) to find the length of a side with the given surface area:

\(\displaystyle a=\sqrt{\frac{SA}{6}}=\sqrt{\frac{72}{6}}=\sqrt{12}=2\sqrt{3}\)

Example Question #1 : Cubes

Find the length of an edge of the following cube:

Length_of_edge

The volume of the cube is \(\displaystyle 27\ m^3\).

 

 

Possible Answers:

\(\displaystyle 3\ m\)

\(\displaystyle 9\ m\)

\(\displaystyle 12\ m\)

\(\displaystyle 6\ m\)

 

\(\displaystyle 15\ m\)

 

Correct answer:

\(\displaystyle 3\ m\)

Explanation:

The formula for the volume of a cube is

\(\displaystyle V=(e)^3\),

where \(\displaystyle e\) is the length of the edge of a cube.

Plugging in our values, we get:

\(\displaystyle 27\ m^3 = (e)^3\)

\(\displaystyle e = 3\ m\)

Example Question #1 : Cubes

Find the length of an edge of the following cube:

Length_of_edge

The volume of the cube is \(\displaystyle 64\ m^3\).

Possible Answers:

\(\displaystyle 8\ m\)

 

\(\displaystyle 6\ m\)

\(\displaystyle 3\ m\)

\(\displaystyle 4\ m\)

\(\displaystyle 5\ m\)

Correct answer:

\(\displaystyle 4\ m\)

Explanation:

The formula for the volume of a cube is

\(\displaystyle V=(e)^3\),

where \(\displaystyle e\) is the length of the edge of a cube.

Plugging in our values, we get:

\(\displaystyle 64\ m^3=(e)^3\)

\(\displaystyle e=4\ m\)

Example Question #1881 : High School Math

What is the length of an edge of a cube that has a surface area of 54?

Possible Answers:

\(\displaystyle 6\)

\(\displaystyle 9\)

\(\displaystyle 3\)

\(\displaystyle 12\)

Correct answer:

\(\displaystyle 3\)

Explanation:

The surface area of a cube can be determined using the following equation:

\(\displaystyle SA=6\times l^2\)

\(\displaystyle 54=6l^2\)

\(\displaystyle \frac{54}{6}=\frac{6l^2}{6}\)

\(\displaystyle 9=l^2\)

\(\displaystyle \sqrt9=\sqrt{l^2}\)

\(\displaystyle 3=l\)

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