The sector COB is cut from the circle with center O. The ratio of the area of the sector removed from the whole circle to the area of the sector removed from the inner circle is R^2/r^2 .

Martha is training for a duathlon, which includes biking and running. she knows that yesterday she covered a total distance of over 55.5 miles in more than than 4.5 hours of training. martha runs at a speed of 6 mph and bikes at a rate of 15.5 mph.