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Everybody uses juxtaposition for multiplication (or dot when some separation is required) and horizontal line for division. * and / are poor man's substitutes

by mich41 14y ago

Everybody uses juxtaposition for multiplication (or dot when some separation is required) and horizontal line for division. * and / are poor man's substitutes when all you have is ASCII. × is used for vector products, Cartesian products and products of algebraic structures in general. The only place I've ever seen × or ÷ being used in arithmetics was primary school. No idea why they use them.

gpvos 14y ago
In primary school in the Netherlands (and maybe elsewhere?), : is used for division.
- mich41 14y ago
  Right, I've seen this one too.
- pyrocrasty 14y ago
  It's actually widely used for division, but only in some contexts. (It signifies a ratio, eg. "3:2 odds".)
mseebach 14y ago
> The only place I've ever seen × or ÷ being used in arithmetics was primary school. No idea why they use them. Perhaps because the other prominent use is on the buttons of every single calculator in the world.
- kps 14y ago
  I recall using × and ÷ in primary school, before the advent of portable calculators. I know that's mere anecdotal evidence, but I believe there do exist reliable documentary sources from that era.
  - mseebach 14y ago
    Clearly, the idea to put those symbols on calculator buttons didn't come from nowhere. I think our collective point is that there exists a separate tradition for using × and ÷.
rmccue 14y ago
÷ is the symbol for division since it symbolises a fraction, with the two dots taking the place of the numbers. I'd say this is why, as some people have noted, : can also be used for division in some contexts: it represents a ratio, which is again just a fraction.
- sesqu 14y ago
  The way I was taught it, though, is that ratios are rather different from fractions. You might say 2:1 of tea and honey, but ⅔ tea and ⅓ honey. However, when describing only one quantity, some people will say 1:2 of honey while others might say 1:3 of honey.
Uncompetative 14y ago
What then happens when you have to split a long line of math? What then happens when you need to multiply 2 by 2? The answer to the first question is that the following line is begun with a multiplication sign. The answer to the second question is that bold roman type is used for vectors and often for other forms of tensor like a matrix to overload the semantics of dot and cross to not be scalar products were either of their arguments in italic.

by mich41 14y ago

gpvos 14y ago

In primary school in the Netherlands (and maybe elsewhere?), : is used for division.

mich41 14y ago
Right, I've seen this one too.
pyrocrasty 14y ago
It's actually widely used for division, but only in some contexts. (It signifies a ratio, eg. "3:2 odds".)

mseebach 14y ago

> The only place I've ever seen × or ÷ being used in arithmetics was primary school. No idea why they use them. Perhaps because the other prominent use is on the buttons of every single calculator in the world.

kps 14y ago
I recall using × and ÷ in primary school, before the advent of portable calculators. I know that's mere anecdotal evidence, but I believe there do exist reliable documentary sources from that era.
- mseebach 14y ago
  Clearly, the idea to put those symbols on calculator buttons didn't come from nowhere. I think our collective point is that there exists a separate tradition for using × and ÷.

rmccue 14y ago

÷ is the symbol for division since it symbolises a fraction, with the two dots taking the place of the numbers. I'd say this is why, as some people have noted, : can also be used for division in some contexts: it represents a ratio, which is again just a fraction.

sesqu 14y ago
The way I was taught it, though, is that ratios are rather different from fractions. You might say 2:1 of tea and honey, but ⅔ tea and ⅓ honey. However, when describing only one quantity, some people will say 1:2 of honey while others might say 1:3 of honey.

Uncompetative 14y ago

What then happens when you have to split a long line of math? What then happens when you need to multiply 2 by 2? The answer to the first question is that the following line is begun with a multiplication sign. The answer to the second question is that bold roman type is used for vectors and often for other forms of tensor like a matrix to overload the semantics of dot and cross to not be scalar products were either of their arguments in italic.