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 - Answers
1. The answer
The diameter is approximately 36 units.
2. The answer
The radius is approximately 72 units.
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units
4. 
units
