Answer: 12πins.
Step-by-step explanation:
Since the area if a circle = πr²
From the question 
Area of the circle = 36πins²
To find the circumference of the circle, we need to find the common radius of the circle and this could be achieved from the area of the circle given above.
 πr² = 36π, solving this gives. Divide through by π
 r² = 36
 r = +/-√36
 = +/-6
Now to find the circumference of the circle, we substitute for r in the formula below.
Circumstances = 2πr
 = 2 ×π × 6
 = 12πins.