The formula for the area of a circle is π r².
The diameter of the circle is twice the radius.
Divide 120 by 2 to get the radius of 60.
60² is 3600.
Multiply 3600 by 3.14 to get 11304.
The circle is 11304 square miles.
There are 100 people per square mile, so multiply that by 100.
1130400 people are within broadcast distance of the radio station.
Hope this helps!
