All GMAT Math Resources
Example Questions
Example Question #816 : Gmat Quantitative Reasoning
A cube is inscribed inside a sphere of volume . Give the surface area of the cube.
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 volume formula:
Twice this, or 12, is the diameter, and, subsequently, the length of a diagonal of the cube. By an extension of the Pythagorean Theorem, if is the length of an edge of the cube,
The surface area is six times this:
Example Question #5 : Calculating The Surface Area Of A Cube
Cube A is inscribed inside a sphere, which is inscribed inside Cube B. Give the ratio of the surface area of Cube B to that of Cube A.
Suppose the sphere has diameter .
Then Cube B, the circumscribing cube, has as its edge length the diameter , and its surface area is .
Also, Cube A, the inscribed cube, has this diameter as the length of its diagonal. If is the length of an edge, then from the three-dimensional extension of the Pythagorean Theorem,
The surface area is , so
.
The ratio of the surface areas is
The correct choice is .
Example Question #101 : Rectangular Solids & Cylinders
The length of one side of a cube is 4 meters. What is the surface area of the cube?
By definition, all sides of a cube are equal in length, so each face is a square, There are six faces on a cube, so its total surface area is six times the area of one of its square faces. If one of its sides is 4 meters, then this will also be the other dimension of one of its square faces, so the total surface area is:
Example Question #101 : Rectangular Solids & Cylinders
Find the surface area of a cube whose side length is .
To solve, remember that the equation for surface area of a cube is:
Example Question #101 : Rectangular Solids & Cylinders
Aperture labs makes a variety of cubes. If each cube has a volume of , what is the surface area of the cube?
Aperture labs makes a variety of cubes. If each cube has a volume of , what is the surface area of the cube?
Let's work backwards from our goal in this question.
We know that we need to find surface area. To find surface area of a cube, we can use the following equation:
Where l is the length of one side.
Next, let's look at the volume formula:
So, we can find our length
Let's leave l like that for the moment, and use it to find our surface area.
Example Question #1 : Calculating The Volume Of A Cube
What is the volume of a cube with a side length of ?
Example Question #102 : Rectangular Solids & Cylinders
The length, width, and height of a rectangular prism, in inches, are three different prime numbers. All three dimensions are between six feet and seven feet. What is the volume of the prism?
It is impossible to tell from the information given.
Six feet and seven feet are equal to, respectively, 72 inches and 84 inches. There are three different prime numbers between 72 and 84 - 73, 79, and 83 - so these are the three dimensions of the prism in inches. The volume of the prism is
cubic inches.
Example Question #3 : Calculating The Volume Of A Cube
The length of a diagonal of one face of a cube is . Give the volume of the cube.
The correct answer is not among the other responses.
A diagonal of a square has length times that of a side, so each side of each square face of the cube has length . Cube this to get the volume:
Example Question #4 : Calculating The Volume Of A Cube
The length of a diagonal of a cube is . Give the volume of the cube.
Let be the length of one edge of the cube. By the three-dimensional extension of the Pythagorean Theorem,
Cube the sidelength to get the volume:
Example Question #5 : Calculating The Volume Of A Cube
A sphere with surface area is inscribed inside a cube. Give the volume of the cube.
The sidelength of the cube is the diameter of the inscribed sphere, which is twice that sphere's radius. The sphere has surface area , so the radius is calculated as follows:
The diameter of the sphere - and the sidelength of the cube - is twice this, or .
Cube this sidelength to get the volume of the cube: