All ISEE Upper Level Quantitative Resources
Example Questions
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:
Example Question #1 : How To Find The Diagonal Of A Cube
What is the length of the diagonal of a cube with a side length of ? Round to the nearest hundreth.
It is easiest to think about diagonals like this by considering two points on a cube (if it were drawn in three dimensions). We could draw it like this:
(Note that not all points are drawn in on the cube.)
The two points we are looking at are:
and
Solve this by using the distance formula. This is very easy since one point is all s. It is merely:
This is approximately .
Example Question #2 : How To Find The Diagonal Of A Cube
What is the length of the diagonal of a cube with a side length of ? Round to the nearest hundreth.
It is easiest to think about diagonals like this by considering two points on a cube (if it were drawn in three dimensions). We could draw it like this:
(Note that not all points are drawn in on the cube.)
The two points we are looking at are:
and
Solve this by using the distance formula. This is very easy since one point is all s. It is merely:
This is approximately .
Example Question #3 : How To Find The Diagonal Of A Cube
What is the length of the diagonal of a cube with a volume of ? Round to the nearest hundredth.
First, you need to find the side length of this cube. We know that the volume is:
, where is the side length.
Therefore, based on our data, we can say:
Solving for by taking the cube-root of both sides, we get:
Now, it is easiest to think about diagonals like this by considering two points on a cube (if it were drawn in three dimensions). We could draw it like this:
(Note that not all points are drawn in on the cube.)
The two points we are looking at are:
and
Solve this by using the distance formula. This is very easy since one point is all s. It is merely:
This is approximately .
Example Question #321 : Geometry
What is the length of the diagonal of a cube with a surface area of ? Round your answer to the nearest hundredth.
First, you need to find the side length of this cube. We know that the surface area is defined by:
, where is the side length. (This is because the cube is sides of equal area).
Therefore, based on our data, we can say:
Take the square root of both sides and get:
Now, it is easiest to think about diagonals like this by considering two points on a cube (if it were drawn in three dimensions). We could draw it like this:
(Note that not all points are drawn in on the cube.)
The two points we are looking at are:
and
Solve this by using the distance formula. This is very easy since one point is all s. It is merely:
This is approximately .
Example Question #21 : Solid Geometry
What is the length of one side of a cube that has a volume of ?
We must begin by using the equation for the volume of a cube:
(It is like doing the area of a square, then adding another dimension!)
We know that the volume is . Therefore, we can rewrite our equation:
Using your calculator, we can find the cube root of . It is . (If you get just round up to . This is a calculator issue!).
This is the side length you need!
Another way you could do this is by cubing each of the possible answers to see which gives you a volume of .
Example Question #322 : Geometry
What is the length of one side of a cube that has a surface area of ?
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.
Now, we know that is ; therefore, we can write:
Solve for :
Take the square root of both sides:
This is the length of one of your sides.
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