A hard disk in a computer rotates 3750 revolutions per minute. What is the angular speed in radian per second?

The rotational speed is (3750 rev)/min. Now 1 rev = 360° = 2π rad, and 1 min = 60 s, so that is equal to (3750 × 2π rad)/(60 s) = (3750 × 2π)/60 rad/s. The expression can be simplified a bit, and can also be replaced by a numerical approximation.