All GRE Math Resources
Example Questions
Example Question #1 : Cubes
What is the length of the diagonal of a cube that has a surface area of ?
To begin, the best thing to do is to find the length of a side of the cube. This is done using the formula for the surface area of a cube. Recall that a cube is made up of squares. Therefore, its surface area is:
, where is the length of a side.
Therefore, for our data, we have:
Solving for , we get:
This means that
Now, the diagonal length of a cube is found by a form of the distance formula that is akin to the Pythagorean Theorem, though with an additional dimension added to it. It is:
, or , or
Now, if the the value of is , we get simply
Example Question #1521 : Gre Quantitative Reasoning
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?
4L3
2L3
8
5L
2L2
2L3
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 #1522 : Gre Quantitative Reasoning
What is the volume of a cube with a surface area of ?
The surface area of a cube is merely the sum of the surface areas of the squares that make up its faces. Therefore, the surface area equation understandably is:
, where is the side length of any one side of the cube. For our values, we know:
Solving for , we get:
or
Now, the volume of a cube is defined by the simple equation:
For , this is:
Example Question #3 : Cubes
The volume of a cube is . If the side length of this cube is tripled, what is the new volume?
Recall that the volume of a cube is defined by the equation:
, where is the side length of the cube.
Therefore, if we know that , we can solve:
This means that .
Now, if we triple to , the new volume of our cube will be:
Example Question #2 : How To Find The Volume Of A Cube
What is the volume of a cube with surface area of ?
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 squares. It is therefore:
For our values, this is:
Solving for , we get:
, so
Now, the volume of a cube is merely:
Therefore, for , this value is:
Example Question #2 : How To Find The Volume Of A Cube
A cube has a volume of 64, what would it be if you doubled its side lengths?
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
.
Doubling the side gives you 8
.
The volume of the new cube would then be 512
.
Example Question #331 : Geometry
A rectangular box is 6 feet wide, 3 feet long, and 2 feet high. What is the surface area of this box?
64 sq ft
72 sq ft
22 sq ft
36 sq ft
48 sq ft
72 sq ft
The surface area formula we need to solve this is 2ab + 2bc + 2ac. So if we let a = 6, b = 3, and c = 2, then surface area:
= 2(6)(3) + 2(3)(2) +2(6)(2)
= 72 sq ft.
Example Question #2 : How To Find The Surface Area Of A Cube
What is the surface area of a rectangular box that is 3 feet high, 6 feet long, and 4 feet wide?
108
144
72
84
96
108
Surface area of a rectangular solid
= 2lw + 2lh + 2wh
= 2(6)(4) + 2(6)(3) + 2(4)(3)
= 108
Example Question #1 : How To Find The Surface Area Of A Cube
A large cube is made by fitting 8 smaller, identical cubes together. If the volume of each of the smaller cubes is 27, what is the surface area of the large cube?
Since the volume of the smaller cubes with edges, , is 27, we have:
.
The large cube has edges .
So the surface area of the large cube is:
.
Example Question #1 : How To Find The Surface Area Of A Cube
Quantity A:
The surface area of a cube with a volume of .
Quantity B:
The volume of a cube with a surface area of .
The relationshp cannot be determined from the information given.
Both quantities are equal.
Quantity A is greater.
Quantity B is greater.
Quantity B is greater.
The relationship can be determined, because it is possible to find the surface area of a cube from the volume and vice versa.
Quantity A:
To find the surface area of the cube, you must find the side length. To find the side length from the volume, you must find the cube root.
Find the cube root of the volume.
Insert into surface area equation.
Quantity B:
To find the volume of a cube, you must find the side length. To find the side length from the surface area, you must divide by 6, then find the square root of the result. Then, cube that result.
Divide by 6.
Square root.
Now, to find the volume.
Quantity B is greater.