Answer:
30.76 
Step-by-step explanation:
To calculate the circumference of a circle you just have to multiply the diameter by pi.
C= D*
And in order to calculate the value of the diameter you have to clear the formula for the area.
A= 
r=
r=
r=4,89
Once we get the radius, we only have to calculate the diameter:
D=2r=9,79
now we just calculate the circumference:
C=D*
= (9.79)(3.14)= 30.76