Talk:Distributivity

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Mathematics rating: Start Class High Priority  Field: Algebra

I have many associates in the accounting field who are baffled when they divide a list of numbers and the sum of those results does not match the dividing the sum of the original numbers. They have to start moving pennys around and they blame their electronic spreadsheets. We all know that division has Distributivity, but the spreadsheet also rounds the numbers, and rounding does not have Distributive property. I was looking for an online reference that could explain this well in language that accountants (not mathamaticians) could understand. Could you help me with this? Is there an article on Non-distributivity? Or could you perhaps provide examples of things that do not have Distributive property? Thanks. -Sandy —The preceding unsigned comment was added by 71.138.248.226 (talk) 00:12, 2 January 2007 (UTC).

I've stuck a few examples into the article (section Distributivity and rounding). Tell me if that helps; if you can find some good references it'd be good to have them here. –EdC 02:32, 2 January 2007 (UTC)

[edit] Division

I'd like to see this article be more clear on whether or not division is distributive over addition. It is, isn't it? But, I was confused about it from reading this article. Distributivity of division over addition is mentioned and invoked as though it were the case, but isn't explained to be so.

Thanks! Cherry Cotton 22:53, 25 April 2007 (UTC)

Division (in the reals) is simply multiplication by the reciprocal (the multiplicative inverse) of the divisor, so distributivity follows immediately. The same holds for the distributivity of multiplication (or division) over subtraction. –EdC 20:40, 26 April 2007 (UTC)
You have to be careful though, because it only works the one way: (1 + 5)/7 = 1/7 + 5/7, but 1/(5 + 7) ≠ 1/5 + 1/7. Hope this helps. 10:11, 24 June 2007 (UTC)
I don't think so, never learned it yet. I'd listen to the above user. Lunakeet 12:05, 2 May 2008 (UTC)

[edit] Image

The bottom part is the above multiplication carried out in two different parts. The top and bottom are equivalent.
The bottom part is the above multiplication carried out in two different parts. The top and bottom are equivalent.

I've removed this image because I think it's not very clear.. I've been looking at it but I've yet to see two multiplications taking place there.. there are four and eight Xs above the line and some more below it but I fail to see how this image clarifies the distributive law. What multiplication is taking place (4 * 2 = 8?) and where's the distributive law? - Simeon (talk) 18:29, 1 June 2008 (UTC)