A.)The circumference of a circle is 2*pi*R where r=radius
in this case, x= radius, 2*pi*X
so to find the perimeter of a semicircle, simply divide it by 2 and add on the diameter of the figure, which is pi*x+2x
B.) Since the perimeter of the shape is 25.71, and it asks you to calculate the radius, simply do 3.142*X+2X=25.71
X(3.142+2)=25.71
X=25.71/(3.142+2)
X=5
