# What is the difference between radius & diameter?

Jan 2, 2016

Diameter is the longest line that you can draw in a circle passing through the centre of the circle.
Radius is the line joining the centre of the circle to any point on the circumference.

#### Explanation:

Diameter is the ratio of the circumference of the circle to the irrational constant 'pi' (3.1415...). Radius is the half of the diameter.

$D = 2 \times r a \mathrm{di} u s \text{ and } r a \mathrm{di} u s = \frac{D}{2}$

Actually pi is defined to be the ratio of the circumference of the circle to the diameter of the circle. Therefore, you can solve for the diameter from that equation.

$\pi = \frac{C}{D} , \text{ or " D = C/pi " or } C = \pi \times D$