All ISEE Upper Level Math Resources
Example Questions
Example Question #7 : Tetrahedrons
A regular tetrahedron comprises four faces, each of which is an equilateral triangle. Each edge has length 16. What is its surface area?
The area of each face of a regular tetrahedron, that face being an equilateral triangle, is
Substitute edge length 16 for :
The tetrahedron has four faces, so the total surface area is
Example Question #1 : How To Find The Surface Area Of A Tetrahedron
In three-dimensional space, the four vertices of a tetrahedron - a solid with four faces - have Cartesian coordinates .
What is the surface area of this tetrahedron?
The tetrahedron looks like this:
is the origin and are the other three points, which are each twelve units away from the origin on one of the three (mutually perpendicular) axes.
Three of the surfaces are right triangles with two legs of length 12, so the area of each is
.
The fourth surface, , has three edges each of which is the hypotenuse of an isosceles right triangle with legs 12, so each has length by the 45-45-90 Theorem. That makes this triangle equilateral, so its area is'
The surface area is therefore
.
Example Question #1 : How To Find The Surface Area Of A Tetrahedron
In three-dimensional space, the four vertices of a tetrahedron - a solid with four faces - have Cartesian coordinates .
In terms of , give the surface area of this tetrahedron.
The tetrahedron looks like this:
is the origin and are the other three points, which are units away from the origin, each along one of the three (perpendicular) axes.
Three of the surfaces are right triangles with two legs of length 12, so the area of each is
.
The fourth surface, , has three edges each of which is the hypotenuse of an isosceles right triangle with legs , so each has length by the 45-45-90 Theorem. That makes this triangle equilateral, so its area is'
The surface area is therefore
.
Example Question #1 : Spheres
There is a perfectly spherical weather balloon with a surface area of , what is its diameter?
There is a perfectly spherical weather balloon with a surface area of , what is its diameter?
Begin with the formula for surface area of a sphere:
Now, set it equal to the given surface area and solve for r:
First divide both sides by .
Then square root both sides to get our radius:
Now, because the question is asking for our diameter and not our radius, we need to double our radius to get our answer:
Example Question #2 : Spheres
A wooden ball has a surface area of .
What is its radius?
Cannot be determined from the information provided
A wooden ball has a surface area of .
What is its radius?
Begin with the formula for surface area of a sphere:
Now, plug in our surface area and solve with algebra:
Get rid of the pi
Divide by 4
Square root both sides to get our answer:
Example Question #3 : Spheres
There is a perfectly spherical weather balloon with a surface area of , what is its radius?
There is a perfectly spherical weather balloon with a surface area of , what is its radius?
Begin with the formula for surface area of a sphere:
Now, set it equal to the given surface area and solve for r:
First divide both sides by .
Then square root both sides to get our answer:
Example Question #1 : Volume Of A Sphere
In terms of , give the volume, in cubic inches, of a spherical water tank with a diameter of 20 feet.
20 feet = inches, the diameter of the tank; half of this, or 120 inches, is the radius. Set , substitute in the volume formula, and solve for :
cubic inches
Example Question #71 : Solid Geometry
A sphere has diameter 3 meters. Give its volume in cubic centimeters (leave in terms of ).
The diameter of 3 meters is equal to centimeters; the radius is half this, or 150 centimeters. Substitute in the volume formula:
cubic centimeters
Example Question #1 : Spheres
A spherical buoy has a radius of 5 meters. What is the volume of the buoy?
A spherical buoy has a radius of 5 meters. What is the volume of the buoy?
To find the volume of a sphere, use the following formula:
All we have to do is plug in 5 meters and simplify:
Example Question #2 : Spheres
You have a ball with a radius of 12 cm, what is its volume?
You have a ball with a radius of 12 cm, what is its volume?
The volume of a sphere can be found via the following formula:
We know our radius, so all we need to do is plug in and simplify:
So we have our answer: