## Prealgebra (7th Edition)

$C=2\times5.9\pi=11.8\pi\approx 11.8\times3.14=37.052$ square km.
The circumference of a circle can be calculated as: $C=2r\pi=d\pi$ where r is the radius and d is the diameter. Here: $r=5.9$ km $C=2\times5.9\pi=11.8\pi\approx 11.8\times3.14=37.052$ square km.