+36916 Circumference of larger circle = pi d = 18 pi
smaller circle = 4 pi
After 20 revolutions the smaller circle travels 20 * 4 pi = 80 pi
18 pi is one complete travel around the larger circle
80 pi - 18 pi *4 = 8pi = the tangent point
8pi /18pi x 360 = 160 degrees.
