A circle with radius of 3 cm sits inside a circle with radius of 7 cm. What is the area of the shaded region? Round your final answer to the nearest hundredth.

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.