Suppose the circumference of a circle is 2 pi what is the area?

 Circumference of a circle = 2 π r 

(where r is the radius) 

Area of a circle = π r^2 

(where r is the radius) 

you have to find the radius

C = 2π unit 
r = 1 unit 

Area = π square units 

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'.

Y=3x+1 so the first one