High School Math : How to find circumference

Example Questions

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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 .

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?