If you notice, the quarter circle has a radius of 10 feet. So you can find the circumference/perimeter by using the formula as normal (2pi*radius) to get 20*pi (2*pi*10 = 20*pi). Divide this by four (since it is a quarter circle) to get 5*pi.
You also notice that if you combine the two semicircles, you get a full circle, which means you can find the perimeter normally (which is 10*pi) 10pi+5pi = 15pi which is approximately 47.1
