Talk:Multiplication

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Removing Bible material whose relevance to multiplication is slim

Multiplication is mentioned in the Bible when God tells Noah to go forth and multiply. (Joke! Really that is a different kind of multiplication.) However, Noah did have to use multiplication when he made the ark, because Genesis 6:15 says:
And this is the fashion which thou shalt make it of: The length of the ark shall be three hundred cubits, the breadth of it fifty cubits, and the height of it thirty cubits.
So Noah knew the ark had to be a volume of 300 times 50 times 30 is 450000 cubics3, to fit two of all the animals in the world in it.

Since the first sentence is acknowledged to be a joke and not to refer to the arithmetic operation, it shouldn't be there.

The Ark example isn't very good, for two reasons. First, in the Bible, the product of the three numbers is not mentioned, so this is not an example of a use of multiplication in the Bible. (It would be very relevant in an article about the three dimensions of ordinary space).

Second, the computation as presented is almost certainly wrong, since the Ark was surely shaped shaped like a boat, not like a rectangular box, and therefore its volume would not have been 450,000 cubits3 but some subtantially smaller number, which cannot be calculated exactly from the given data. Dpbsmith 20:02, 22 March 2007 (EDT)

Multiplication table

This article should have the multiplication table ("times table"). I suppose that the generic child using Conservapedia already knows it, but having it for review purposes can't harm. In addition (pun not intended!), the table makes it easier to understand the whole concept of multiplication. Unfortunately, I'm completely wiki-ignorant, and don't know how to insert tables in articles. SilvioB 20:47, 30 August 2008 (EDT)

I think that's a very good idea... maybe I'll try to put something together. Human 17:28, 31 August 2008 (EDT)

Retreading previous material?

Didn't this article used to be longer? I was just putting in some stuff about the symbols used, and it seemed a bit deja vu. Was there a reason for deleting some of this article, and did I miss it? Didn't mean to re-add that which was decided was inappropriate... Human 18:15, 31 August 2008 (EDT)

Illustrations and examples

How about a diagram? I've taught multiplication to several children of one-digit age by showing them rows of objects. Like, 2 rows of 6 eggs is 12 (a dozen eggs) or three groups of two coins make 6 coins. Counting by twos is a cheap way to get started on multiplying (and by the way learning your two times table); see times table.

Don't be in a hurry to get all formal and grad schoolish. We need to give our readers practical knowledge. --Ed Poor Talk 21:36, 1 September 2008 (EDT)

Can you find and upload a picture of a carton of eggs for us to use? That would be cool. Human 16:47, 3 September 2008 (EDT)

Symbol

Several conventions are used to indicate multiplication.

  • For simple numbers, the symbol (\times) used looks much like the letter "X", as in the examples above.
  • Since the "X" looks like a letter, and letters are commonly used in algebra to indicate unknowns, or variables, the "dot" is frequently used: A • B = B • A.
  • Alternatively a period may be used to denote multiplication
  • Also, in algebraic use, quantities are simply juxtaposed to indicate that they are to be multiplied:
Y = 3aX + 4bZ

Please rewrite the above content, which I just now removed from the article. (Do you know how to use article history? --Ed Poor Talk 08:16, 3 September 2008 (EDT))

I don't really see anything wrong with that content. What is confusing about it? Philip J. Rayment 10:04, 3 September 2008 (EDT)
In the UK when I was at school, a long time ago before the liberals ruined education with "modern math", it used to be the convention that X was the symbol for multiplication and x was the symbol for an unknown quantity.Malakker 10:08, 3 September 2008 (EDT) (sorry, hit the wrong button first time.)Malakker 10:08, 3 September 2008 (EDT)
An asterisk * is often sometimes used for multiplication (and / for division), especially on computer systems such as Microsoft Excel, although I have also seen it in printed documents as well. I believe (although I may be wrong) that this originates from its use in early computer programming languages such as BASIC. Sideways 10:39, 3 September 2008 (EDT)
Yes, that should be added to the list. I actually used it in place of the dot when I was writing the above while I went and searched for the code for the "dot product" symbol. And, yes, the 'sterisk goes back at least to BASIC. I think it's mostly because the dot isn't in the basic ASCII character set (also, it's not on your keyboard...). By the way, who added the incorrect "parentheses" example at the end of the article? Human 16:46, 3 September 2008 (EDT)

If someone can explain how multiplication is used in algebra, then a tiny note about * or "dot" may be in order. But not before. --Ed Poor Talk 20:04, 3 September 2008 (EDT)

I thought the "target" age group was "college bound high school age students"? Human 20:39, 3 September 2008 (EDT)
You thought right. Now stop blathering and do some writing. I want that on my desk in the morning, Jimmy Olsen, or by Great Caesar's Ghost I'll know the reason why! --Ed Poor Talk 20:43, 3 September 2008 (EDT)
I think Human might have meant through his question that if this article was intended for college bound high school age students, explaining the use of multiplication in algebra would be unnecessary. It would be assumed that most people in that age group and at that educational level would have learned the basics of algebra long ago. ZTak 21:32, 3 September 2008 (EDT)
"Now stop blathering and do some writing." - I don't know if that was supposed to be a joke? I was writing, what I added got edited a bit (what is above is partly wrong...), and then moved here to discuss. Perhaps you (Ed) could write at least an outline of what you envision this article covering? Better yet, as a math teacher, surely you could write it with one hand tied behind your back while being pelted with spitballs? Human 19:14, 4 September 2008 (EDT)

Math rendering

Is there a problem with the rendering of the math mark-up? For me (in both IE and Firefox) the expression following "Likewise" is much larger than the previous examples despite having identical mark-up tags. BrianCo 17:09, 4 September 2008 (EDT)

Looks fine to me (Firefox). However, before Ed's "force rendering" edit, the expression after "Likewise" looked slightly smaller, so I'd assume that that edit is the key to the size issue. But don't ask me why it's fine for me now while not for you. Check the version before Ed's edit - do the lines look the same to you there? --DirkB 17:37, 4 September 2008 (EDT)
It still looked different in both Firefox and IE so I removed the slash at the end and it renders OK now. BrianCo 16:56, 5 September 2008 (EDT)
You maybe missed the part where I said that the version you just restored makes the lower line look significantly smaller for me at least. I mean, it's nice that it renders okay for you now, but I believe that we should rather investigate the cause of this instead of playing a rendering tug-o-war ;) --DirkB 17:00, 5 September 2008 (EDT)
I just removed the second line while streamlining that paragraph. Sort of a blunt solution, but I think it's the most appropriate one since this is an entry about multiplication and not commutativity. --DirkB 17:10, 5 September 2008 (EDT)

Numbers vs Real numbers

Typically students learn addition and multiplication with Natural numbers. Then come Integers, Rational and Real numbers. For a student it is important to know that those are the most well known commutative operations with numbers. Why would you restrict the field and confuse their mind with "real numbers" only? Huh. --BillP 16:15, 5 September 2008 (EDT)

I'm not sure I see your point. Why do you insist on replacing a clear and precise statement with a fuzzy one? The way it reads now, multiplication of complex numbers is included in this, which is borderline wrong because multiplication of complex numbers is most definitely not well-known to anybody but the more advanced math students. --DirkB 16:58, 5 September 2008 (EDT)
Edit: I just solved this the trivial way. See my last edit to this article. I think that this should be an acceptable compromise. --DirkB 17:09, 5 September 2008 (EDT)
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