The formula for the arclength of a circle of radius R and angle A (in radians) is Arclength=AR. Note that when we have a full turn, i.e. the whole perimeter of the circle, A=2pi and the Arclength is the familiar formula for the perimeter of a circle P=2piR. Thus, given that the angle is A=4rad and the radius is R=30ft we have that the arclength is AR=4*30=120ft