Circumference and Area of a Circle
To calculate the circumference (which is like perimeter) and the area of a circle, you need a special irrational number: pi. Pi is the ratio of the circumference of a circle to its diameter. Watch this lecture series to explore the circumference and area of circles, and complete the interactive exercises.
Practice
Circumference of a circle - Questions
1. A circle has a circumference of 
units.
What is the diameter of the circle?
_______ units
2. A circle has a circumference of 
units.
What is the radius of the circle?
_______ units
3. What is the circumference of the following circle?
_______ units
4. Suppose the diameter of a circle is 
units. What is its circumference?
_______ units