The dartboard above is made up of three concentric circles with radii 1, 3, and 5. Assuming that a dart thrown will land randomly on the dartboard, what is the probability that it lands in the green region?
+36916 Red area = pi x r^2 = pi (1^2) = pi
Green area = pi r^2 - the red area = 9 pi - pi = 8 pi
Blue area = pi r^2 - green - red areas = 25pi - 8pi - pi = 16 pi
Total area is pi r^2 = 25 pi (16pi + 8pi + pi)
green area is 8 pi
8pi/25pi = 8/25
