# What is the relationship between pi, radius, diameter and circumference?

##### 1 Answer
Sep 21, 2015

The constant pi is the ratio between a circle's circumference and its diameter.

#### Explanation:

The circumference of a circle is given by the equation

C = 2 * pi * r

Where C is the circumference, pi is pi, and r is the radius. The radius is equal to one half of the diameter of a circle and measures the distance from the center of the circle to the edge of the circle.

By rearranging the above equation, we see that the constant pi can be defined by:

pi = C / (2 * r)

And since the radius is equal to half of the diameter, we can write

pi = C / d

Where d = diameter of the circle.

Hope this helps!