In terms of diameter (d), the area (A) of a circle is given by A = (π/4)d² For your larger circle ... A = (π/4)*(24 km)² A = 144π km² . . . . . . . . area of larger circle
For your smaller circle ... A = (π/4)*(8 km)² A = 16π km² . . . . . . . . . area of smaller circle
The ratio of the two areas is (larger area)/(smaller area) = ((π/4)*(24 km)²) / ((π/4)*(8 km)²) = (24/8)² . . . . . . . . . . . . π/4, km cancel, so it simplifies to this = 3² = 9 . . . . . . this many small circles have the same area as the larger circle
Changing km to ft does not change the ratio of areas.
