# Basic Geometry : How to find circumference

## Example Questions

1 2 3 4 5 6 7 8 9 10 12 Next →

### Example Question #111 : How To Find Circumference

The area of a circle is . What is the circumference?

Explanation:

The area of a circle is , so in this case the radius squared is 4. Since the square root of 4 is 2, the radius has length 2. To find the circumference, use the formula . In this case,

### Example Question #112 : How To Find Circumference

The radius of the circle shown here is  units long. What is its circumference?

Explanation:

The formula for the circumference  of a circle given its radius  is . For the circle given in the problem,  units, and so

.

Hence, the circumference of this circle is  units.

### Example Question #111 : How To Find Circumference

A circle has diameter 20.

True or false: The circumference is greater than 60.

True

False

True

Explanation:

The circumference of a circle is its diameter multiplied by , so, since the diameter is 20, the circumference is . Also,

,

so, multiplying both sides by 20 by the Multiplication Property of Inequality,

and

.

The circumference is indeed greater than 60.

### 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?