Circle (C)

A circle with radius R and center C is the set of all points in the plane whose distance from C is R. The area of a circle of radius R is $\pi R^2$, and the perimeter of such a circle is $2\pi R$.

Exercises

1.

What is the area of a circle whose radius is 2 feet?

2.

What is the perimeter of a circle whose radius is 2 meters?

3.

What is the radius of a circle whose area is 12 square feet?

4.

What is the radious of a cirlce whose perimeter is 9 meters?

5.

Suppose that radius of a circle is doubled? What happens to its perimeter? What happens to its area?

6.

By what proportion should I increase the radius of a circle to triple its area?