a) Take prop Inches diameter divided by 12 for feet diameter.
b) Multiply by Pi (i.e. 3.142) for circle distance feet per rev.
c) Multiply by RPM (for tip's distance moved per minute)
d) divide by 60 to get tip speed in feet per second !
The speed of sound at sea level is 1100 ft/second -- Compare !
Hope that is O.K.
mike hallam.