Find the angle Length in radians

Question

S=20feet and radius= 5 feet

Answer 1

S = rθ is the arc length formula but it only works for angles in radian measure. But in this you are asked for radian measure. So if S = rθ then θ = S/r then just plug in the S and the r making sure they are both in the same units (which they are (they are both in feet) to get θ = 20/5 = 4 radians