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 parts of circles - Answers
1. The answer
The area of the shape is \(3 \pi\) units \(^{2}\).
(Note that we could also multiply 3 by \(3.14\) to get \(9.42\) units \(^{2}\).)
2. The answer
The area of the semicircle is \(12.5 \pi\) units \(^{2}\).
(Note that we could also multiply \(12.5\) by \(3.14\) to get \(39.25\) units \(^{2}\).)
3. The answer
The area of the semicircle is \(4.5 \pi\) units \(^{2}\).
(Note that we could also multiply \(4.5\) by \(3.14\) to get \(14.13\) units \(^{2}\).)
4. The answer
The area of the shape is \(12 \pi\) units \(^{2}\).
(Note that we could also multiply 12 by \(3.14\) to get \(37.68\) units \(^{2}\).)