When you have factors in shapes you must remember:
circumference and perimeter are in one unit measures
area is in squared units
volume is in cubed units
So, when the circumference of A is 4 times that of C there is a factor of 4.
Since we need to know the area the factor 4 will change to a factor of 4² since area is a squared unit.
The solution is 4²=16, the are of circle A is sixteen times the area of circle B.
