If the area of a circle is 136.45, what is it's circumference?

The area of a circle = pi * radius squared. so if the area = 136.45, start by dividing by pi to get about 43.43. this means the radius squared = 43.43. square root both sides to get about 6.59 = radius of the circle. the circumference can be found by multiplying the diameter * pi. since the diameter = the radius * 2, we know the diameter of the circle is 13.18. multiply by pi to find the circumference, which would be about 41.41.