GRE Math : How to find the volume of a cube

Study concepts, example questions & explanations for GRE Math

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Example Questions

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

What is the volume of a rectangular box that is twice as long as it is high, and four times as wide as it is long?

Possible Answers:

8

2L3

4L3

5L

2L2

Correct answer:

2L3

Explanation:

The box is 2 times as long as it is high, so H = L/2. It is also 4 times as wide as it is long, so W = 4L. Now we need volume = L * W * H = L * 4L * L/2 = 2L3.

Example Question #1 : Cubes

What is the volume of a cube with a surface area of \(\displaystyle 150\) \(\displaystyle in^2\)?

Possible Answers:

\(\displaystyle 5\:in^3\)

\(\displaystyle 25\:in^3\)

\(\displaystyle 325\:in^3\)

\(\displaystyle 150\:in^3\)

\(\displaystyle 125\:in^3\)

Correct answer:

\(\displaystyle 125\:in^3\)

Explanation:

The surface area of a cube is merely the sum of the surface areas of the \(\displaystyle 6\) squares that make up its faces. Therefore, the surface area equation understandably is:

\(\displaystyle SA = 6*s^2\), where \(\displaystyle s\) is the side length of any one side of the cube. For our values, we know:

\(\displaystyle 150=6s^2\)

Solving for \(\displaystyle s\), we get:

\(\displaystyle 25=s^2\) or \(\displaystyle s=5\)

Now, the volume of a cube is defined by the simple equation:

\(\displaystyle V=s^3\)

For \(\displaystyle s=5\), this is:

\(\displaystyle V=5^3=125\:in^3\)

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

The volume of a cube is \(\displaystyle 64\:in^3\). If the side length of this cube is tripled, what is the new volume?

Possible Answers:

\(\displaystyle 1024\:in^3\)

\(\displaystyle 924\:in^3\)

\(\displaystyle 192\:in^3\)

\(\displaystyle 768\:in^3\)

\(\displaystyle 1728\:in^3\)

Correct answer:

\(\displaystyle 1728\:in^3\)

Explanation:

Recall that the volume of a cube is defined by the equation:

\(\displaystyle V=s^3\), where \(\displaystyle s\) is the side length of the cube. 

Therefore, if we know that \(\displaystyle V=64\), we can solve:

\(\displaystyle 64=s^3\)

This means that \(\displaystyle s=4\).

Now, if we triple \(\displaystyle s\) to \(\displaystyle 12\), the new volume of our cube will be:

\(\displaystyle V=12^3 = 1728\:in^3\)

Example Question #331 : Geometry

What is the volume of a cube with surface area of \(\displaystyle 384\:in^2\)?

Possible Answers:

\(\displaystyle 256\:in^3\)

\(\displaystyle 224\:in^3\)

\(\displaystyle 64\:in^3\)

\(\displaystyle 512\:in^3\)

\(\displaystyle 984\:in^3\)

Correct answer:

\(\displaystyle 512\:in^3\)

Explanation:

Recall that the equation for the surface area of a cube is merely derived from the fact that the cube's faces are made up of \(\displaystyle 6\) squares. It is therefore:

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

For our values, this is:

\(\displaystyle 384=6s^2\)

Solving for \(\displaystyle s\), we get:

\(\displaystyle 64=s^2\), so \(\displaystyle s=8\)

Now, the volume of a cube is merely:

\(\displaystyle V=s^3\)

Therefore, for \(\displaystyle s=8\), this value is:

\(\displaystyle V=8^3=512\:in^3\)

Example Question #24 : Solid Geometry

A cube has a volume of 64, what would it be if you doubled its side lengths?

Possible Answers:

\(\displaystyle 128\)

\(\displaystyle 512\)

\(\displaystyle 256\)

\(\displaystyle 500\)

\(\displaystyle 64\)

Correct answer:

\(\displaystyle 512\)

Explanation:

To find the volume of a cube, you multiple your side length 3 times (s*s*s).  

To find the side length from the volume, you find the cube root which gives you 4 

\(\displaystyle (\sqrt[3]{64})\).  

Doubling the side gives you 8 

\(\displaystyle (4*2=8)\).  

The volume of the new cube would then be 512 

\(\displaystyle (8*8*8=512)\).

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