# High School Math : How to find circumference

## Example Questions

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### Example Question #71 : Radius

A circle has a diameter of 13 cm.  What is the circle's circumference?      Explanation:

To find the circumference of a circle, multiply the circle's diameter by .

### Example Question #72 : Radius

Find the circumference of the following circle:       Explanation:

The formula for the circumference of a circle is ,

where is the radius of the circle.

Plugging in our values, we get:  ### Example Question #5 : How To Find Circumference

A car tire has a radius of 18 inches. When the tire has made 200 revolutions, how far has the car gone in feet?

3600π

600π

300π

500π

600π

Explanation:

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 #1 : How To Find Circumference

A circle has the equation below. What is the circumference of the circle?

(x – 2)2 + (y + 3)2 = 9     Explanation:

The radius is 3. Yielding a circumference of .

### Example Question #11 : 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?      Explanation:

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 2 Next → 