Math
posted by sadf .
If a CD spins at 75 revolutions per minute, hoe long, in seconds, does it take for the CD to rotate through an angle of 1125 ?

75 rev/min.
V = (75 / 60) rev/s * 360 deg/rev = 450
deg/s.
t = 1125 deg / 450 deg/s = 2.5 Seconds.