Compute velocity pressure using the formula:

V= 4005 x VP, where

V= velocity, feet per minute (fpm)

VP = velocity pressure, inch in water gauge

Compute cross sectional area of a circular duct using formula:

AREA = r²; where:r = the radius of the duct; 2r = d; d = diameter

Compute volumetric Flow Rate using the formula:

Q = VA, where

Q = flow rate (ft3/ min or M3/min)

V = Velocity (ft/min or m/min)

A = cross sectional area (ft2 or m2)

What is the size of a square duct if the flow rate is 500 CFM and the velocity pressure is 0.1 inches of water gauge?