Don Guinn wrote: > When in the forth or fifth grade my teacher was trying to explain the > difference between pencil leads "2 1/2" verses those rated at "2.5". It > went something like this: Pencils with a lead of "2 1/2" meant that the > hardness was somewhere between "2 1/4" and "2 3/4", where a hardness of > "2.5" meant it was between "2.45" and "2.55". I seem to remember seeing > some pencils with a hardness of "2 2/4" also. I couldn't tell any > difference on how the pencils worked. > > I remember something about a convention which has been lost with the > advent of computers of writing a number, say "2.5" implied that the > measurement was good to a tenth, where "2.500" implied it was good to a > thousant. >
I recall this convention too. You see a variant in old science fiction books, where accuracy is stated in terms like "nine nines". I believe the difference in pencil designations, while a good illustration, is a way of avoiding trademark issues. Best wishes, John ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
