# How do you find the circumference and area of a circle with diameter of 12 inches?

The circumference of a circle is $S = 2 \pi r$ where r =radius
The area of cirlce is $A = \pi {r}^{2}$
The diameter is twice the radius $d = 2 r \implies r = 6$

So the circumference is $S = 12 \pi$ inches
And the area $A = 36 \pi$

Sep 20, 2015

$C = 38 \text{in}$
$A = 113 {\text{in}}^{2}$

#### Explanation:

To find circumference when diameter is known, use the equation $C = \pi \times d$

$C = \pi \cdot 12 \text{in"=38"in}$

To find the area of a circle, use the formula $A = \pi \cdot {r}^{2}$, where $r$ is the radius, which half of the diameter. $r = \frac{1}{2} d = \frac{1}{2} \cdot 12 \text{in"=6"in}$.

A=pi*(6"in")^2"="113"in"^2