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# multiplication

## multiplication

(OP)

There are at least three symbols to denote multiplication: the middle dot as in a·b, the asterisk (a*b) and the cross (a×b). My question: what is the experts' preference?

### RE: multiplication

I guess if you never wrote any programs you'd naturally opt for the algebraic convention of (axb) but if you have, then perhaps the (a*b) would start to look and feel more appropriate.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.

### RE: multiplication

None of the above for symbolic variables and variables with constants:

a times b = ab
6 times z = 6z
etc...

For expressions with all constants (numerals), here is the requirement from IEEE Style Guide:

A multiplication sign (×), not the letter “x” or a multidot (·), should be used to indicate multiplication of
numbers and numerical values, including those values with units (e.g., 3 cm × 4 cm).

So 6 times 3 will be 6 × 3

The dot and cross should be used only when representing matrix functions, except that the dot should also be used in compound unit expressions:

N·m
in·lb
etc...

Them's the rules I gots to follow. But then my grammar are perfect and I would never allow myself to spuriously split an infinitive.

Best to you,

Goober Dave

Haven't see the forum policies? Do so now: Forum Policies

### RE: multiplication

Just a word of warning. I was writing out the students' notes for a week long training course one time and used the "proper" multiplication symbol "×" (Alt+0215, U+00D7) in all the equations.

I printed out two dozen copies, double sided, in color, about 100 pages for each copy... and then I discovered that the printer (or printer driver) didn't recognize that particular symbol and left a gap instead.

### RE: multiplication

I occasionally have that happen with one or more of:

° Ω Δ ÷ μ Σ ® ± ¼ ½ © ƒ ≥ ≤ √ ß ± ¼ ½ ƛ Ø 

The eng-tips font handler or TGML or whatever you call it got all of them right except the last one. It should be a lowercase sigma. I'll put it in here with the TGML code: σ

Best to you,

Goober Dave

Haven't see the forum policies? Do so now: Forum Policies

### RE: multiplication

Stick to *, the X or x is commonly used to indicate cross product.

Fe (IronX32)

### RE: multiplication

I use a lot of parentheses with the dot multiplier in between. None of the stuff I do includes matrix manipulation so dot products and cross products are not really an issue. I use MathType for all equations in Word or PowerPoint and would never include an integer times an integer within an equation (I'm calling BS on the whole confusing a dot multiplier with a decimal point).

I keep running into problems with the IEEE juxtaposition technique with the common symbol for "specific gravity" in my industry being "SG". If I regularly said x times y = xy, then my students would be justified in thinking "SG = S times G" or "kg = k times g". It may be dumb to have a 2 character variable, but that is the way this industry does it.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

### RE: multiplication

Before anyone jumps me, I know that "kg" is actually "grams times 1000", but I do a lot of adiabatic gas work and in the U.S. "k" is the ratio of specific heats, and "g" is the acceleration of gravity (gm is used for "gram"). "kg" is either obviously a unit or incomprehensible as an equation, context is not always enough.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

### RE: multiplication

@david, "BS" is B*S, or B.S ?

@oklhydro, you sound like a guy who'd check that the degree sign is not a superscript "o", again

Quando Omni Flunkus Moritati

### RE: multiplication

I am not sure if you are applying this to your technical papers/reports, but if so, symbols shouldn't be used when conveying information to a layperson. For example, 2-by-4-inch should be used instead of 2"x4". If you aren't, feel free to ignore! :)

Before you doing anything creative, make sure the code likes the artwork you are trying to wow the world with.

### RE: multiplication

In some countries the multiplication is also represented by the normal dot . like: a.b

When using the United States - International keyboard layout the traditional multiplication sign is obtained with RIGHT ALT + [=] = ×

Personally, i do not like * because that is the Excel(TM) solution, not recognized by math.

In algebra it is traditional to avoid the multiplication sign altogether: a.b.c = abc

For grade school students it is perhaps clearer to use a×b, for high school and college perhaps no sign is ok, so I would say it depends on the audience and the intent.

saludos.
a.

### RE: multiplication

Matrix-based mathematical engines will often distinguish between element-wise and matrix operations:

x*y % Full matrix multiplication
x.*y % Element-wise multiplication

No single system is transferable from paper to computer. Or even between mathematical engines.

- Steve

### RE: multiplication

While I can understand how someone would like to 'blame' Excel (I suspect that you're actually blaming Mircosoft), your ire is misplaced. The '*' has been used as a 'programmers' multiplication sign for a lot longer than Excel, or for that matter, Microsoft has been around.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.

### RE: multiplication

I took a Fortran class in 1977 or 1978. Multiplication used "*" and exponentiation used "**".

==========
"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

### RE: multiplication

FORTRAN was using that same convention when I took my first programming class back in 1969, so if longevity counts for anything...

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.

### RE: multiplication

there is also the parenthesis, which is like the nothing:

ab is a times b

(x-y)(z=b)

but to answer your question, I'm not sure I'm some expert, just an experienced practitioner. Also, I use all of these symbols.

f-d

¡papá gordo ain’t no madre flaca!

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