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

Area of a circle - Answers

1. A \approx 25 \pi

A \approx 78.5 unit ^{2}



2. A=16 \pi

3. A=25 \pi



4. A \approx 1 \pi

A \approx 3.14 unit ^{2}



5. A=4 \pi



6. A=4 \pi



7.  A \approx 9 \pi

A \approx 28.26 unit ^{2}