Talk:Ancient Egyptian multiplication

Name change to Ethiopian Multiplication
Evidence: http://www.youtube.com/watch?v=Nc4yrFXw20Q, a documentary on the method that refers to this name. --Paddy (talk) 13:14, 29 July 2010 (UTC)
 * We're descriptivist, not prescriptivist -- that is, we go with what it is most commonly called, not what it should be called. DS (talk) 13:09, 28 August 2010 (UTC)
 * And that is described where? --Paddy (talk) 15:40, 28 August 2010 (UTC)

Generic name
This method is also known by its generic name as double-and-add and is related to the square-and-multiply exponentiation. Lauri.pirttiaho (talk) 18:07, 17 September 2011 (UTC)

Inexact formulation
In the decomposition secion, the sentence "The Egyptians knew empirically that a given power of two would only appear once in a number." makes little mathematical sense. You could rewrite it as "The E. knew empirically that a number had a unique decomposition as sum of powers of two, each power appearing at most once." — Preceding unsigned comment added by 92.102.109.34 (talk) 22:01, 12 December 2014 (UTC)

Background information matches another site
The Background information section is almost exactly word-for-word from this archived page. As the webpage mentions Wikipedia, it's unclear to me which source is the original text. Paul2520 (talk) 02:01, 19 March 2015 (UTC)

A neat point about this method
Ancient Egyptian multiplication really shines if you use a base that is a power of two, especially hexadecimal (as has been noted in a post by icarus on the DozensOnline forum, which I can't link to because of the blacklist). This is because it makes repeated multiplication by two cycle after a few steps to the same number with an extra zero at the end, viz.:


 * 1 → 2 → 4 → 8 → 10
 * 3 → 6 → c → 18 → 30
 * 5 → a → 14 → 28 → 50
 * 7 → e → 1c → 38 → 70
 * 9 → 12 → 24 → 48 → 90
 * b → 16 → 2c → 58 → b0
 * d → 1a → 34 → 68 → d0
 * f → 1e → 3c → 78 → f0

You'd of course also have to memorize the binary decomposition of the digits:

I'd prefer saving hexadecimal to octal, because octal is small enough that memorizing the multiplication table is easy, but this may not be the case for hexadecimal. Furthermore, hexadecimal is more symmetrical than octal, as it is 22 2, unlike octal's non-binary 23. The whole binary mindset seems more consistent in hexadecimal than octal, and so hexadecimal may lend itself better to a thoroughly binary-based algorithm like Ancient Egyptian multiplication.

For example, suppose you want to calculate f6 × 4e. Note that 4e = 40 + 8 + 4 + 2, and then:

1    f6  2    1ec 4   3d8 8   7b0 10   f60 20  1ec0 40  3d80 4e  4af4

So we see that this may be a thoroughly efficient algorithm for a base like hexadecimal. Unfortunately, no culture seems to have realized this and moved to hexadecimal for this algorithm, which is rather a pity, because it means that this observation cannot be included on WP – unless, of course, someone has noted this somewhere (perhaps in a hexadecimal-advocacy publication?). Double sharp (talk) 05:45, 1 April 2015 (UTC)

External links modified
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External links modified (January 2018)
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Background information
I deleted that section: it was merged in in 2014 from Egyptian multiplication and division, and already the talk page there discusses the suspicion that this is mostly WP:OR. Yes, of course it is, it was created by User:Milogardner in 2009, who seems to be the one driving the developments discussed in it. But whether or not it is original research, it definitely is, first, much too detailed for Wikipedia, and second, for the most part it discusses fractions, which perhaps is appropriate for the initial article on multiplication and division, but not for the specific algorithm discussed here. Also most if not all of the references would have to go, leaving it again with only a single reference to a web page, but of course I did not go through each single one to verify whether it does have to say something about the algorithmic part of multiplication. Seattle Jörg (talk) 20:45, 12 October 2020 (UTC)

Cleanup?
- «cleanup, removing how to, footnotes»
 * Why did you remove examples? I disagree that any clean-up is necessariy here. WP:HOWTO.6 is not applicable to significant examples if they illustrate the subject. I'm going to revert this back.

AXO NOV (talk) ⚑ 12:36, 19 December 2021 (UTC)

There was a template saying this article is written like a how to guide, so I fixed it. If you want to revert it, I suggest you manually remove the template as well. Spiritoftheeast1993 (talk) 16:58, 19 December 2021 (UTC)