We had a bit of heated discussion at lunch time today about the right position of the decimal point.
Is it in the middle line or the on baseline between unit and tenth ie 1・5, OR 1.5?

In the text books, maths dictionaries we have at home show the decimal point at the base line like a full stop 1.5, but my husband says it has been international convention to place it in the middle line eg 1・5, and that this was how he was taught 40 years ago. ( 1.5 means 1x5= (1*5) and 1・5 means 1 point 5 (1 1/2)

I suppose it is much simpler for children to learn 1.5 way as they see on a calculator, in textbooks, in most dictionaries. We have settled that we will use the baseline method for decimal point to make our daughter's like simpler!

Any mathematicians here to comment??

It should be in the middle. If it's at the bottom then that means multiply in mathematics.

so instead of saying a x b = c you can write a.b = c

So it's important to put the decimal point higher up

edit - thinking about it, it's probably the use of computers that has forced it down because there is no decimal point on the keyboard so we use the full stop instead. And I've just checked on my spreadsheets and it too formats it at the bottom. Shame on you microsoft!

Not sure it matters, although I could look up some books later. It could be that with electronic media the point moved down from the middle to the bottom. In context there is unlikely to be confusion between 1.5 as a decimal and 1.5 meaning 1 times 5.

How on earth did you manage to get the dot in the middle ? That's very clever . . .

Your husband is right, in the middle.

Oh, it is my Mac doing that for me, it can do these, too:
♩ ♪ ♫♬♭♮ 𝄀𝄡 𝄐 𝄑 𝄑 𝄇 𝄆 𝄪 𝄫 𝄁 𝄂
Now where were we..... yes, decimal point....

WOW !

If you want to type in a decimal point using the keyboard, you can. Press the Alt button, then type in 0183 using the numpad.

Like so: 1?5

Car Expert

EDIT: Of course on these forums, it doesn't work...

EDIT2: My name's got smaller - what's going on here...

That assumes you have a numberpad, which many laptops don't and there seems to be no way of getting the characters without (that I have found), unless you copy and paste them from a word document.

Or use Character Map.

Car Expert

Interesting. Not ever having had anyone tell me one way or the other, I have always put my dot-multiplier (when multiplying matricies, for example) nice, big and round... in middle!



(so as to distinguish it from the decimal points which I would always write at the bottom).

I like your big and round in the middle for multiplier....
like this maybe...

1.5●3=4.5

Does anybody here use "✽" instead of "x" ? ( I guess not )

I do, but I'm a programmer

Ditto

And slash through zeros...

...doesn't everyone when typing (as opposed to writing)? I have never ever seen the decimal place higher up, To me a dot in the middle means multiplication unequivocally, actually that's how I always write it. "." is a decimal point, "x" is either a variable or a cross product.

Ran this question past maths nerd husband and his take on it was :

the decimal point goes low down, so it's in line with the comma for thousands etc. i.e. 2,000.5

(my older son - also maths nerd - obviously learnt to write this as 2 000,5 so his decimal dot is low, to replace the comma)

and that mid-way dots equal multiplication signs BUT that he never uses dots for in that sense when there are numbers involved because it is so ambiguous and that maths very rarely uses multiplication signs anyway because ab already means a times b, no sign needed.

All very curious . . .

Yes, Hanonmum has expressed the gist. Obviously my comments were for handwritten maths, although as also said, I will often leave any indication of a multiplication out altogether. Its interesting though that when faced with a yucky partial differential equation to solve analytically, or something equally nasty, one of my first steps will be to write it out with dots or other multiplaction signs (x's or even brackets) to make to clearer what is actually related to what, and how.

I distinguish my multiplication times signs from my variable or constant x's by using x for the multiplication, and a 'x' written like two c's back to back as a variable (or pick another letter, there is the whole of the greek and cyrillic alphabet to run through, after all).

I wonder how LaTeX, or MatLab display these things.... *goes to experiment*

LaTeX has a different typeface for the "x" that is multiplication, and the dot is in the middle of the height of the letters. I spend a lot of time fiddling with LaTeX in the day job....