If the circumference of a circle is 2 pi what is the radius

C = 2 * pi * r

Plug in what we know:

2pi = 2 * pi * r

Divide 2 pi to both sides:

r = 1

(Remember, anything divided by itself is equal to 1)

A = pi * r^2

Plug in what we know:

A = pi * 1^2

A = pi * 1

A = 1 pi

So the area is '1 pi' or just 'pi'.
 

C=2pir
r=radius
c=circumference

given
c=2pi
2pi=c=2pir
2pi=2pir
divide both sides by 2pi
1=r
radius is 1 unit