wrote in message
...
If they've got to 16 or 18 without realising there are imperial
measurements, I doubt they're about to get any knowledge anywhere.

I can imagine that nowadays, the imperial system is dismissed with a few
throwaway phrases like "Years ago, there used to be other units called feet,
inches, ounces, pounds etc, but they were a pain to work with because they
were related by conversion factors that weren't 10. Be aware that they
exist, and be prepared to convert to/from them if necessary, but treat them
as folk units."

Any system which doesn't even have an integer relationship between
volumetric and linear measurement is a bit dodgy: there are 277.419 cubic
inches in a (UK) gallon. For some reason, there are exactly 231 cubic inches
in a US gallon, which is odd because I thought the conversion between UK and
US was 0.8 UK gall = 1 US gall since the US pint is 16 rather than 20 fluid
ounces. Ah: I see now - the US and UK fluid ounces are slightly different
sizes. It's like troy, avoirdupois and apothecaries ounces all over again -
different trades define their units in slightly different ways. A bit of a
mess!