# Circumference

The circumference is the distance around a circle.

The formula for a circumference is:

where c = circumference and d = diameter or the width of the circle

or

where c = circumference and r = radius which is half the diameter. The radius is the distance from any point on the circle to the center of the circle.

Pi is usually given the value of 3.14 Sometimes you will be asked to just write Pi and other times you will be asked multiply it out.

Watch the math video below for a detailed explanation!

### Practice Math Problems

Assume that = 3.14 and round to 2 decimal places.

- The radius of a circle is 4. What is the circumference ?
- The radius of a circle is 6. What is the circumference ?
- The radius of a circle is 10. What is the circumference ?
- The diameter of a circle is 13. What is the circumference?
- The diameter of a circle is 16. What is the radius ?
- The circumference of a circle is 43.96. What is the radius ?
- The circumference of a circle is 81.64. What is the diameter?