The use of a wind-powered energy is becoming more and more prevalent around the world to produce clean energy. a windmill with a blade 30 feet long rotates at a rate of 45 revolutions per minute. find the angular velocity of the blade.

Remark
This really belongs in physics.  However, it can be done here. The angular velocity does not have anything to do with the length of the blade,

ω = 2π radians / time which will give you radians 
ω = 2π * 45 rpm 
ω = 90 π radians / minute. 

This usually is expressed as radians per second
ω = 90 π / 60  radians / second
ω = 1.5 π radians / second.