The diameter of the circular region is 15 miles
that gives radius = 7.5 miles
Now,
Area = π r² = 3.14 * 7.5* 7.5
= 176.625 mile²
Population density = number of people / land area
this is =
Now rounding off to nearest whole number, we get 9908
So, there are 9908 population living in per square mile.