GMAT Math : Cubes

Study concepts, example questions & explanations for GMAT Math

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Example Questions

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Example Question #1 : Calculating The Volume Of A Cube

A sphere with volume  is inscribed inside a cube. Give the volume of the cube.

Possible Answers:

Correct answer:

Explanation:

The sidelength of the cube is the diameter of the inscribed sphere, which is twice that sphere's radius. The sphere has volume , so the radius is calculated as follows:

The diameter of the sphere - and the sidelength of the cube - is twice this, or 6. Cube this sidelength to get the volume of the cube:

Example Question #2 : Calculating The Volume Of A Cube

The distance from one vertex of a cube to its opposite vertex is twelve feet. Give the volume of the cube.

Possible Answers:

Correct answer:

Explanation:

Since we are looking at yards, we will look at twelve feet as four yards.

Let  be the length of one edge of the cube. By the three-dimensional extension of the Pythagorean Theorem, 

 yards.

Cube this sidelength to get the volume:

 cubic yards.

Example Question #3 : Calculating The Volume Of A Cube

An aquarium is shaped like a perfect cube; the area of each glass face is  square meters. If it is filled to the recommended  capacity, then how much water will it contain? 

Note:  cubic meter  liters.

Possible Answers:

The correct answer is not given among the other choices.

Correct answer:

Explanation:

A perfect cube has square faces; if a face has area 6.25 square meters, then each side of each face measures the square root of this, or 2.5 meters. The volume of the tank is the cube of this, or

 cubic meters.

Its capacity in liters is  liters.

80% of this is 

 liters. 

Example Question #111 : Rectangular Solids & Cylinders

Which choice comes closest to the volume of a cube with surface area  square centimeters?

Possible Answers:

Correct answer:

Explanation:

The suface area of a cube is six times the square of the length of one side, so solve for  in the following:

This is the sidelength in centimeters; since we are looking at meters, divide this by 100 to convert to  meters.

Cube this to get volume

 cubic meters.

Of the given choices, 3.5 cubic meters comes closest.

Example Question #31 : Cubes

The distance from one vertex of a cube to its opposite vertex is one foot. Give the volume of the cube.

Possible Answers:

Correct answer:

Explanation:

Since we are looking at inches, we will look at one foot as twelve inches.

Let  be the length of one edge of the cube. By the three-dimensional extension of the Pythagorean Theorem, 

 inches.

Cube this sidelength to get the volume:

 cubic inches.

Example Question #11 : Calculating The Volume Of A Cube

A cubic pool is usually filled at about  of its total volume. If one side of the pool is m, how many liters of water will fill the pool to the desired capacity?

Possible Answers:

Correct answer:

Explanation:

To find the volume of a cube we use the formula:

In our case the total volume of the pool is 10cubic meters.

Filling the pool to 95% of its total volume will require:  cubic meters.

Now we need to convert from cubic meters to liters in order to answer the question.

Remember  cubic meter =  liters.

Thus,

.

Therefore, the number of liters of water needed is 950000 liters.

 

Example Question #12 : Calculating The Volume Of A Cube

A sphere of surface area  is inscribed inside a cube. Give the volume of the cube.

Possible Answers:

The correct answer is not given among the other responses.

Correct answer:

Explanation:

The diameter of a sphere is equal to the length of an edge of the cube in which it is inscribed. We can derive the radius using the formula for the surface area of a sphere:

Substituting in the given value:

Dividing each side by :

Taking the square root of each side:

The diameter is twice this, or . This is the length of the edge of the cube, so we can cube it to get the volume:

Example Question #111 : Rectangular Solids & Cylinders

A sphere with surface area  circumscribes a cube. Give the volume of the cube.

Possible Answers:

The correct answer is not given among the other responses.

Correct answer:

The correct answer is not given among the other responses.

Explanation:

The diameter of a sphere is equal to the length of a diagonal of the cube it circumscribes. We can derive the radius using the formula for the volume of a sphere, but first, we have to solve for the radius using the formula for the surface area of a sphere:

The diameter is twice this, or . This is the length of the diagonal of the cube. By the three-dimensional extension of the Pythagorean Theorem,

 

The volume is the cube of this:

, which is not given as one of the choices.

Example Question #601 : Geometry

A cube has a volume of  cubic feet. If the length of each side of the cube is doubled, what is its new volume, in cubic feet?

Possible Answers:

Correct answer:

Explanation:

One way we can solve this problem is by first determining the dimensions of the original cube. By definition, the length, width, and depth of a cube are equal, so if the original volume is 8 cubic feet, then:

We then double the length of each side of the original cube, so the length of each side of the new cube is:

Now we can use the dimensions of our new cube to find its volume:

So if we double the dimensions of the original cube, the resulting cube has a volume that is eight times greater, 64 cubic feet.

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