How do you find the circumference of a circle if you have the area?

-- Take the formula for the area of a circle:

Area = (pi) (radius)2

-- Divide each side by (pi):

Area/pi = (radius)2

-- Take the square root of each side:

Radius = sqrt(area/pi)

-- Take the formula for the circumference of a circle:

Circumference = (pi) x (diameter) = (pi) x (2 x radius)

-- Where it says "radius", substitute the expression for the radius

from two lines above:

Circumference = (pi) x 2 x sqrt(area/pi)

or

Circumference = 2 x sqrt(pi x area)

Look at that ! That's exactly what you asked for.