v = rw
where; v = velocity , r = radius , w = angular speed
you're given the diameter = 0.5 miles so the radius = 0.25 miles
180 = (0.25)w
180/0.25 = w
720 radians per hour = w
2pi radians in 1 revolution
720 rad/hr * 1 rev / 2pi rad = 720/2pi rev/hr
= 114.6 rev/hr
