Answer:
16pi mi
Explanation:
The smallest circumference for a given area is that of a circle with that area. The area is given by ...
A = πr²
so we can find r as ...
64π = πr²
r = √64 = 8 . . . . miles
The circumference of this circle is ...
C = 2πr = 2π·(8 mi) = 16π mi
The circumference of the area is at least 16π miles.
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If the shape is not constrained to a circle, the circumference can be anything you like.