All ISEE Upper Level Quantitative Resources
Example Questions
Example Question #1 : How To Find The Surface Area Of A Cube
The volume of a cube is 343 cubic inches. Give its surface area.
The volume of a cube is defined by the formula
where is the length of one side.
If , then
and
So one side measures 7 inches.
The surface area of a cube is defined by the formula
, so
The surface area is 294 square inches.
Example Question #5 : Cubes
What is the surface area of a cube with side length ?
Recall that the formula for the surface area of a cube is:
, where is the length of a side of the cube. This equation is easy to memorize because it is merely a multiplication of a single side () by because a cube has equal sides.
For our data, we know that ; therefore, our equation is:
Example Question #3 : How To Find The Surface Area Of A Cube
What is the surface area of a cube with a volume ?
To solve this, first calculate the side length based on the volume given. Recall that the equation for the volume of a cube is:
, where is the side length.
For our data, this gives us:
Taking the cube-root of both sides, we get:
Now, use the surface area formula to compute the total surface area:
, where is the length of a side of the cube. This equation is easy to memorize because it is merely a multiplication of a single side () by because a cube has equal sides.
For our data, this gives us:
Example Question #1 : How To Find The Surface Area Of A Cube
What is the surface area of a cube with a volume ?
To solve this, first calculate the side length based on the volume given. Recall that the equation for the volume of a cube is:
, where is the side length.
For our data, this gives us:
Taking the cube-root of both sides, we get:
(You will need to use a calculator for this. If your calculator gives you something like . . . it is okay to round. This is just the nature of taking roots!).
Now, use the surface area formula to compute the total surface area:
, where is the length of a side of the cube. This equation is easy to memorize because it is merely a multiplication of a single side () by because a cube has equal sides.
For our data, this gives us:
Example Question #5 : How To Find The Surface Area Of A Cube
What is the surface area for a cube with a diagonal length of ?
Now, this could look like a difficult problem; however, think of the equation for finding the length of the diagonal of a cube. It is like the Pythagorean Theorem, just adding an additional dimension:
(It is very easy, because the three lengths are all the same: ).
So, we know this, then:
To solve, you can factor out an from the root on the right side of the equation:
Just by looking at this, you can tell that the answer is:
Now, use the surface area formula to compute the total surface area:
, where is the length of a side of the cube. This equation is easy to memorize because it is merely a multiplication of a single side () by because a cube has equal sides.
For our data, this is:
Example Question #6 : How To Find The Surface Area Of A Cube
What is the volume of a cube with a diagonal length of ?
Now, this could look like a difficult problem. However, think of the equation for finding the length of the diagonal of a cube. It is like the Pythagorean Theorem, just adding an additional dimension:
(It is very easy, because the three lengths are all the same: ).
So, we know this, then:
To solve, you can factor out an from the root on the right side of the equation:
Just by looking at this, you can tell that the answer is:
Now, use the equation for the volume of a cube:
(It is like doing the area of a square, then adding another dimension!).
For our data, it is:
Example Question #7 : How To Find The Surface Area Of A Cube
What is the surface area of a cube with a volume of ?
We know that the volume of a cube can be found with the equation:
, where is the side length of the cube.
Now, if the volume is , then we know:
Either with your calculator or with careful math, you can solve by taking the cube-root of both sides. This gives you:
This means that each side of the cube is long; therefore, each face has an area of , or . Since there are sides to a cube, this means the total surface area is , or .
Example Question #2 : How To Find The Surface Area Of A Cube
What is the surface area of a cube that has a side length of ?
This question is very easy. Do not over-think it! All you need to do is calculate the area of one side of the cube. Then, multiply that by (since the cube has sides). Each side of a cube is, of course, a square; therefore, the area of one side of this cube is , or . This means that the whole cube has a surface area of or .
Example Question #9 : How To Find The Surface Area Of A Cube
What is the surface area of a cube on which one face has a diagonal of ?
One of the faces of the cube could be drawn like this:
Notice that this makes a triangle.
This means that we can create a proportion for the sides. On the standard triangle, the non-hypotenuse sides are both , and the hypotenuse is . This will allow us to make the proportion:
Multiplying both sides by , you get:
To find the area of the square, you need to square this value:
Now, since there are sides to the cube, multiply this by to get the total surface area: