trigonometry
posted by Marie :) .
If a flywheel is 3 feet in diameter and if a belt over the wheel is traveling at the rate of 3000 feet per minute, find the number of revolutions of the wheel per minute.

same kind of problem here
http://www.jiskha.com/display.cgi?id=1314932124
Just change the numbers 
actually a bit different, ....
one rotation covers 3π feet
number of rotations = 3000/(3π) = 1000/π or appr 318.3 times per minute
check:
318.3 rmp times 3π = 3000 feet