If the diameter is 1/2 mile, that is 0.5 mile, then the radius is 0.25 -half of it!
the angular speed is theta/time, which means
w=theta/time
but another formula for it is Velocityradians
w=velocityradians
velocity is 180 mph and radians are (revolution/2\(\pi\) radius), that is:
w=180(1/2\(\pi\)0.25)
and if we calculate this, we have: w=114.59, which is the correct answer!