Answer: choice A) 18.9 km
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Work Shown:
Use the given area A = 28.3 to find the radius r
A = pi*r^2
28.3 = 3.14*r^2
3.14*r^2 = 28.3
r^2 = 28.3/3.14
r^2 = 9.01273885350319 approximately
r = sqrt(9.01273885350319)
r = 3.00212239149292
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Which is then used to find the circumference
C = 2*pi*r
C = 2*3.14*3.00212239149292
C = 18.8533286185756
C = 18.9