add/sub axis of rota. when calc. volume of rotation

[Parkstrailer]

I've seen many examples of volume of rotation problems off the y=0 and x=0 axis . . and I am totally confused as to whether add or subtract the axis of rotation when determining radius. For example (outer radius - inner radius), I found one site that said its always((axis of rotation - outer radius) - (aor - inner radius)) but then I've found sites that are adding it after?!?! So confused, please help! thx

[stapel_eliz]

It might help if you posted a specific example, or provided links to explanations you feel are contradictory. That way, the volunteers can have a chance to "see" what you're talking about.

Thank you!