The volume of a cylinder with respect to its diameter is:
V=(hπd^2)/4, and we are told that the height is 3r, r=d/2, so 3r=3d/2=h
V=(3d/2)(πd^2)/4
V=(3πd^3)/8, we know d=10 so
V=3000π/8
V=375π in^3, lastly we are told to approximate π≈3.14 so
V≈375(3.14) in^3
V≈1177.5 in^3