input/output rpm ratio

[crosstown]

I have an electric motor turning 1775 rpm, driving a speed/torque reducer with a 37.5-1 ratio. There is an 8 inch pulley on the output shaft which steps up to a 12 inch pulley on my conveyor headspool. What are the rpms on my 12 inch sheave and what is the rule of thumb to figure this out next time? thank you

 

[dvd]

1775/(reducer ratio)*(driveR sprocket pitch diameter)/(driveN sprocket pitch diameter) = RPM at conveyor head shaft