Ann in Houston wrote:

Do your calculations treat the bottle
as
a full cylinder, or did you stop at the top of the neck? That could
make
a real difference too. Thanks for being intrigued enough to check it
out.

I treated it as an exact cylinder - if I wanted to figure out the
difference
due to curvature, I'd actually have emptied the contents into a proper
measuring container, as otherwise I'd have to take into account the
curvature on the bottom, the tapering on the top, the size of the neck (at
least, the one I used had some water in the neck), and the thickness of
the
plastic (which looks like it probably isn't even uniform). It's a lot
easier to make assumptions :-) (besides which, since I couldn't get an
exact measurement, it was all rough anyway). In fact, either our water
supplier is cheating us, or the jug is actually a little bigger than my
calculation, because it should really be about 1150 cu.in. for a 5 (US)
gallon container.
--
derek

I certainly wouldn't have bothered to figure out the neck and all. The real
question was whether or not 12 cubic inches could hold 7.5 gallons. I
appreciate you doing it the way you did.