All High School Math Resources
Example Questions
Example Question #122 : Plane Geometry
This figure is a circle with a radius of 3 cm.
What is the circumference of the circle (cm)?
In order to find the circumference of a circle (which is the perimeter or distance around the circle), you must double the radius and multiply by pi ().
Example Question #72 : Radius
What is the circumference of a circle with a radius of 4?
The equation for the circumference of a circle is , so by substituting the given radius into the equation, we get .
Example Question #11 : How To Find Circumference
A circle has a diameter of 13 cm. What is the circle's circumference?
To find the circumference of a circle, multiply the circle's diameter by .
Example Question #12 : How To Find Circumference
Find the circumference of the following circle:
The formula for the circumference of a circle is
,
where is the radius of the circle.
Plugging in our values, we get:
Example Question #201 : Basic Geometry
A car tire has a radius of 18 inches. When the tire has made 200 revolutions, how far has the car gone in feet?
600π
500π
300π
3600π
600π
If the radius is 18 inches, the diameter is 3 feet. The circumference of the tire is therefore 3π by C=d(π). After 200 revolutions, the tire and car have gone 3π x 200 = 600π feet.
Example Question #51 : Plane Geometry
A circle has the equation below. What is the circumference of the circle?
(x – 2)2 + (y + 3)2 = 9
The radius is 3. Yielding a circumference of .
Example Question #1 : How To Find Circumference
Ashley has a square room in her apartment that measures 81 square feet. What is the circumference of the largest circular area rug that she can fit in the space?
In order to solve this question, first calculate the length of each side of the room.
The length of each side of the room is also equal to the length of the diameter of the largest circular rug that can fit in the room. Since , the circumference is simply
Example Question #1 : How To Find The Length Of The Diameter
What is the diameter of a circle with a circumference of ?
To find the diameter we must understand the diameter in terms of circumference. The equation for the circumference of a circle is , where is the circumference and is the diameter. The circumference is equal to the diameter multiplied by .
We can rearrange to solve for .
All we have to do is plug in the circumference and divide by , and it will yield the diameter.
The s cancel and the diameter is .
Example Question #281 : Plane Geometry
If the area of a circle is four times larger than the circumference of that same circle, what is the diameter of the circle?
4
32
16
8
2
16
Set the area of the circle equal to four times the circumference πr2 = 4(2πr).
Cross out both π symbols and one r on each side leaves you with r = 4(2) so r = 8 and therefore d = 16.
Example Question #1 : Diameter
The perimeter of a circle is 36 π. What is the diameter of the circle?
3
36
72
18
6
36
The perimeter of a circle = 2 πr = πd
Therefore d = 36
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