physics
posted by mymi .
The motor of a fan turns a small wheel of radius rm = 1.60 cm.This wheel turns a belt, which is attached to a wheel of radius rf = 2.90 cmthat is mounted to the axle of the fan blades. Measured from the center of this axle, the tip of the fan blades are at a distance rb = 11.0 cm.When the fan is in operation, the motor spins at an angular speed of รน = 1200 rpm. What is the tangential speed of the tips of the fan blades?

tangential velocity = (blade radius)*w
where w is the angular velocity of the fan blades (not the motor) in radians/s. Get it from the motor's rpm and the ratio 2.90/1.60. That is the ratio of motor rpm to blade rpm in this case. 
Thanks for the help drwls. I got the correct answer, but the ratio was suppose to be 1.60/2.90.

You are quoting the inverse rotary speed ratio, blade/motor. It all depends upon whether you multiply or divide the factor. We do not disagree.