Oops -- I was likening it to UPS here in the US.  They consider volume weight 
to be L+H+D, so I was calculating the best volume/price to be a cube of 
L=H=D.



On Monday 11 June 2007 22:29, jamesp@intertex.net wrote:
>  For a given volume, you can't simply divide by 3.  You'd have to take the
> cube root of that volume to get the correct dimension.
>
> Jim
>
> > I would think a cube.  For a given volume-weight, divide by 3 and make
> > a cube  of that dimension on each side.
> >
> > On Monday 11 June 2007 06:08, Russell McMahon wrote:
> >> A diversion for those who can be bothered:
> >>
> >> Kristin is studying in Australia.
> >> The weather is getting cold lately.
> >> Russell & Valerie want to send her a box full of clothes, eiderdown,
> >> text books and more.
> >> The largest box that can be sent by parcel post is
> >>
> >>     Largest side <= 1000 mm
> >>     Sum of L +     2 x (D + H)  <= 2000 mm = Volume.weight = VW
> >>
> >>         L     length
> >>         D    depth
> >>         H    Height
> >>
> >> True volume is of course L x D x H
> >>
> >> Assignment for students:
> >>
> >>
> >>                 What box dimensions maximise the true volume that can
> >> be sent?
> >>                 Assume a rectangular box.
> >>
> >>                 Report time to solve.
> >>
> >>
> >> The answer seems somehow obvious in retrospect but was annoyingly
> >> unintuitive (to me).
> >>
> >> Clue - of sorts:        John Crook will tell me that the answer is
> >> obvious on inspection using information theory (he'll be right).
> >>
> >>
> >>
> >>
> >>             Russell
> >>
> >>
> >>
> >>
> >> _____________________________
> >>
> >> Notes:
> >>
> >> 1.    I sent the parcel this evening - all 17.7 kg of it.
> >>
> >> 2.    Volume.Weight is actually a mongrel measure that is neither
> >> volume per weight.
> >>
> >> 3.    2 x (D+H) is the "girth" - the distance around the box.
> >> They seem to do it this way because they can do it with a pencil and
> >> paper (or in their head) more easily than using multiplication.
> >> What they REALLY want is volume.
> >> The ideal shape (from a sender's point of view) maximises the true
> >> volume per volume.weight.
> >>
> >> ie              maximises     L x D x H / ( L + 2x(D+H))
> >>
> >> However, for a fixed volume.weight, maximising volume does just as
> >> well so maximising
> >>
> >>     L x D x H while keeping
> >>
> >>         L + 2 x (D+H) = 2000 mm does the same thing.
> >>
> >> 4.    We had a nice black plastic box with lid, plastic clip in
> >> rollers and dimensions that *just* exceeded the allowable maximum VW
> >> if you took the very outer measurements in each case. As this was
> >> handles etc, and as the cross section was a trapezoid that was
> >> substantially smaller than D x H so true VW was well under the limit,
> >> it clearly met the spirit of the rules and MAY have met the letter
> >> depending on the mood of the clerk concerned. I used it. They didn't
> >> bother measuring it.
> >
> > --
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