# What is the radius of a circle whose diameter is 13 units?

##### 1 Answer
Nov 28, 2015

$\frac{13}{2}$ units or $7.5$ units

#### Explanation:

The diameter can expressed with the formula:

$d = 2 r$

where:
d = diameter
r = radius

This means that the diameter is double the length of the radius. To find the radius, do:

$d = 2 r$
$13 = 2 r$
$\frac{13}{2} = r$

$\therefore$, the radius is $\frac{13}{2}$ units or $7.5$ units.