To find the volume of the cylinder we multiply the area of the face by the height of the cylinder. Area pi*r^2
First find area
768in^3/3in = 256in^2
Pi*r^2 = 256
r^2 = 256 / pi
radius = root of 256/pi
Hence radius = 9.027033337 in
To check answer
Pi*9.027033337^2 * 3in = 768in^3
Finalized answer to 2 d.p
Radius = 9.03 in