Re: Too narrowly defined: DIVISION SIGN & COLON

Philippe Verdy, Tue, 10 Jul 2012 13:50:03 +0200:
> 2012/7/10 Leif Halvard Silli:
>> Asmus Freytag, Mon, 09 Jul 2012 19:32:47 -0700:
>>> The European use (this is not limited to Scandinavia)
>>
>> Thanks. It seems to me that that this tradition is not without a link
>> to the (also) European tradition of *not* using the DIVISION SIGN (÷)
>> for division.
>
> Why European ?

We have 3 accounts which say that is European: I, Jukka and Asmus. It
might be spread wider ... But perhaps your point was that it is more
narrow? ;-)

> I never heard before this discussion that the DIVISION
> SIGN (÷) would be used to mean a substraction.

I was about to say that the ÷ is only used as to signify an
independent, negative number. E.g. on a thermometer and other places
where the negative number stands on its own. For instance, in PR
material (÷50%!), then that is how it is used. But then I looked up a
small book on the almanac from 1920,[1] written by a head teacher in
mathematics, and he uses ÷ everywhere. E.g. from page 16: 26 ÷ 12 = 14.

Btw, I also checked with the mathematical works of Niels Henrik Abel,
from first half of the 19th century. And he did not seem to use the ÷
symbol at all. Not as subtraction symbol, not as negative number symbol
and not as division symbol. You can check his works yourself - they are
mostly in French.[2]

> And I leave in Europe.
> This sign was even the first one I learned for the division at school
> when I was a child, long before the slash (/), and later the colon (:)
> essentially for noting scale ratios on maps.

I have no recollection of when I learned the DIVISION SIGN (÷) as
division sign. But I have a recollection of asking someone about what
that sign meant when used on a calculator ... Today I am probably more
than 4 times as old as when I asked that question - and it is all a bit
in the haze ... But I am quite certain that I learned its meaning as
subtraction symbol before I learned about its meaning as DIVISION
symbol. (I started to attend school in the mid 1970-ties.) The only
thing I am 100% certain about, regardless of what meaning we learned,
is that we did not learn to write the (handwritten) ÷ symbol.

[1] http://books.google.no/books?id=HpoAcgAACAAJ&dq
[2] http://www.abelprize.no/c54178/seksjon/vis.html?tid=54179

-- 
Leif Halvard Silli