All GRE Math Resources
Example Questions
Example Question #2 : How To Find The Surface Area Of A Prism
Kate wants to paint a cylinder prism.
What is the surface area of her prism if it is inches tall and has a diameter of inches? Round to the nearest whole number.
First, find the area of the base of the cyclinder:
and multiply that by two, since there are two sides with this measurement: .
Then, you find the width of the rectangular portion (label portion) of the prism by finding the circumference of the cylinder:
. This is then multiplied by the height of the cylinder to find the area of the rectanuglar portion of the cylinder: .
Finally, add all sides together and round: .
Example Question #1511 : Gre Quantitative Reasoning
This triangular prism has a height of feet and a length of feet.
What is the surface area of the prism? Round to the nearest tenth.
Find the area of the triangular sides first:
Since there are two sides of this area, we multiply the area by 2:
Next find the area of the rectangular regions. Two of them have the width of 3 feet and a length of 7 feet, while the last one has a width measurement of feet and a length of 7 feet. Multiply and add all other sides:
.
Lastly, add the triangular sides to the rectangular sides and round:
.
Example Question #1 : How To Find The Volume Of A Prism
A rectangular prism has a width of 3 units, a length that is twice the width, and a height that is two-thirds the length. What is the volume of the prism?
Remember, the formula for the volume of a rectangular prism is width times height times length:
Now, let's solve the word problem for each of these values. We know that . If length is double the width, then the length must be 6 units. If the height is two-thirds the length, then the height must be 4:
Multiply all three values together to solve for the volume:
The volume of the rectangular prism is units cubed.
Example Question #1 : How To Find The Length Of An Edge Of A Prism
The surface area of a rectangular prism is , and the lengths of two sides are and . What is the volume of the prism?
The surface area of a rectangular prism with sides , , and is given as:
.
Two sides are known; it does not matter how they are designated, but for this problem let and , with as the unknown side. This yields equality:
Now that the three dimensions are known, it's possible to calculate the volume:
Example Question #1511 : Gre Quantitative Reasoning
Quantity A: The length of a side of a cube with a volume of .
Quantity B: The length of a side of a cube with surface area of .
Which of the following is true?
Quantity B is larger.
Quantity A is larger.
The two quantities are equal
The relationship between the two quantities cannot be determined.
The two quantities are equal
Recall that the equation for the volume of a cube is:
Since the sides of a cube are merely squares, the surface area equation is just times the area of one of those squares:
So, for our two quantities:
Quantity A
Use your calculator to estimate this value (since you will not have a square root key). This is .
Quantity B
First divide by :
Therefore,
Therefore, the two quantities are equal.
Example Question #1 : How To Find The Length Of An Edge Of A Cube
What is the length of an edge of a cube with a surface area of ?
The surface area of a cube is made up of squares. Therefore, the equation is merely times the area of one of those squares. Since the sides of a square are equal, this is:
, where is the length of one side of the square.
For our data, we know:
This means that:
Now, while you will not have a calculator with a square root key, you do know that . (You can always use your calculator to test values like this.) Therefore, we know that . This is the length of one side
Example Question #1513 : Gre Quantitative Reasoning
If a cube has a total surface area of square inches, what is the length of one edge?
There is not enough information given.
There are 6 sides to a cube. If the total surface area is 54 square inches, then each face must have an area of 9 square inches.
Every face of a cube is a square, so if the area is 9 square inches, each edge must be 3 inches.
Example Question #1512 : Gre Quantitative Reasoning
The surface area of a cube is 486 units. What is the distance of its diagonal (e.g. from its front-left-bottom corner to its rear-right-top corner)?
None of the others
9
9√(3)
9√(2)
81
9√(3)
First, we must ascertain the length of each side. Based on our initial data, we know that the 6 faces of the cube will have a surface area of 6x2. This yields the equation:
6x2 = 486, which simplifies to: x2 = 81; x = 9.
Therefore, each side has a length of 9. Imagine the cube is centered on the origin. This means its "front-left-bottom corner" will be at (–4.5, –4.5, 4.5) and its "rear-right-top corner" will be at (4.5, 4.5, –4.5). To find the distance between these, we use the three-dimensional distance formula:
d = √((x1 – x2)2 + (y1 – y2)2 + (z1 – z2)2)
For our data, this will be:
√( (–4.5 – 4.5)2 + (–4.5 – 4.5)2 + (4.5 + 4.5)2) =
√( (–9)2 + (–9)2 + (9)2) = √(81 + 81 + 81) = √(243) =
√(3 * 81) = √(3) * √(81) = 9√(3)
Example Question #2 : How To Find The Diagonal Of A Cube
You have a rectangular box with dimensions 6 inches by 6 inches by 8 inches. What is the length of the shortest distance between two non-adjacent corners of the box?
The shortest length between any two non-adjacent corners will be the diagonal of the smallest face of the rectangular box. The smallest face of the rectangular box is a six-inch by six-inch square. The diagonal of a six-inch square is .
Example Question #2 : How To Find The Diagonal Of A Cube
What is the length of the diagonal of a cube with side lengths of each?
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