Let's note the units given for 
, it's in rev/s. In the last section,
and most everything we'll do from now on, we'll want to work in radians.
So we should first do the appropriate conversion
Our problem gives the initial and final angular velocity, and the number
of revolutions that the fan rotated. That looks like a job for
eqn. 1.20. Setting 
and solving
for 
we have
