Question

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.

Answer 1

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.