## Friday 31 January 2014

### Lies, Damned Lies, and Something About Statistics

In a long passed discussion about quotations on the AP Statistics news group the quotation, “There are three kinds of lies; lies, damned lies, and statistics.” came up. The quote is usually attributed to either Mark Twain or Disraili, and several nice notes regarding the veracity of the quote, and its origin, were contributed. Here are snips and direct quotes from the ones that seemed most interesting…

Chris Olsen waded in with this:

“I was reading something or other recently -- I don't remember what it was, but do remember it was a statistician writing -- and he alluded to this quote. In the following the [] are my interjections. What the statistician said was that Disraeli was arguing for or against [I kind of think against] the repeal of the Corn Laws in the English Parliament [possibly in 1846]. An individual [Robert Peel?] on the other side pointed out some sort of statistic in arguing the other side of the issue, and that is when Disraeli is alleged to have made the damn remark.“

David Bee added a source for a slightly different version of the quote:

“…on Page 242 of their compilation 'Statistically Speaking' (1996), compilers CC Gaither and AE Cavazos-Gaither have the following, attributed to Disraeli in George Seldes's 1960 book The Great Quotations: There are lies, damn lies, and church statistics.”

Rex Bogg’s contributed a link to HYPERLINK "http://www1c.btwebworld.com/quote-unquote/" Quote-Unquote , a web site with the radio articles of Nigel Rees. About the topic in question, he writes:

“Although sometimes attributed to Mark Twain – because it appears in his posthumously-published Autobiography (1924) – this should more properly be ascribed to Disraeli, as indeed Twain took trouble to do: his exact words being, ‘The remark attributed to Disraeli would often apply with justice and force: “There are three kinds of lies: lies, damned lies, and statistics”.’

On the other hand, the remark remains untraced among Disraeli’s writings and sayings and Lord Blake, Disraeli’s biographer, does not know of any evidence that Disraeli said any such thing and thinks it most unlikely that he did. So why did Twain make the attribution? A suggestion: Leonard Henry Courtney, the British economist and politician (1832-1918), later Lord Courtney, gave a speech on proportional representation ‘To My Fellow-Disciples at Saratoga Springs’, New York, in August 1895, in which this sentence appeared: ‘After all, facts are facts, and although we may quote one to another with a chuckle the words of the Wise Statesman, “Lies - damn lies - and statistics,” still there are some easy figures the simplest must understand, and the astutest cannot wriggle out of.’

It is conceivable that Twain acquired the quotation from this - and also its veiled attribution to a ‘Wise Statesman’, whom he understood to be Disraeli. The speech was reproduced in the (British) National Review, No. 26, in the same year. Subsequently, Courtney’s comment was reproduced in an article by J.A. Baines on ‘Parliamentary Representation in England illustrated by the Elections of 1892 and 1895’ in the Journal of the Royal Statistical Society, No. 59 (1896): ‘We may quote to one another with a chuckle the words of the Wise Statesman, lies, damn lies, and statistics, still there are some easy figures which the simplest must understand but the astutest cannot wriggle out of.’ It would be a reasonable assumption that Courtney was referring to Disraeli by his use of the phrase ‘Wise Statesman’, though the context in which the phrase is used is somewhat complicated. For some reason, at this time, allusions to rather than outright quotations of Disraeli were the order of the day (he had died in 1881). Compare the fact that the remark to an author who had sent Disraeli an unsolicited manuscript – ‘Many thanks; I shall lose no time in reading it’ – is merely ascribed to ‘an eminent man on this side of the Atlantic’ by G.W.E. Russell in Collections and Recollections, Chap. 31 (1898).

Comparable sayings: Dr Halliday Sutherland’s autobiographical A Time to Keep (1934) has an account of Sir Henry Littlejohn, ‘Police Surgeon, Medical Officer of Health and Professor of Forensic Medicine at the University [Edinburgh] ... Sir Henry’s class at 9 a.m. was always crowded, and he told us of the murder trials of the last century in which he had played his part. It was Lord Young [judge] who said, “There are four classes of witnesses - liars, damned liars, expert witnesses, and Sir Henry Littlejohn”.’ Lies, Damn Lies, and Some Exclusives was the title of a book about British newspapers (1984) by Henry Porter. ‘There are lies, damned lies ... and Fianna Fáil party political broadcasts’ - Barry Desmond MEP, (Irish) Labour Party director of elections, in November 1992.

## Tuesday 21 January 2014

### Circles and Equilateral Triangles

One blog I follow regularly is Antonio Gutierrez's gogeometry. If you teach/study/like plane geometry he should be one of your regular references.

Recently among his posts have been a couple with a related theme, circles inscribed or circumscribed about an equilateral triangle. I'm listing these because they are each a wonderful relationship, and together give these otherwise somewhat mundane seeming triangles a luster students?teachers/others might miss.

I will post the problems, but not the proofs, which (if you can't/won't work them out yourself you can find at the links provided to Antonio's site.

So on we go...

1) draw a circle and inscribe an equilateral triangle. Now pick any point on the circumference and construct segments from this point to the three vertices. The sum of the lengths of the two shorter segments will equal the third. The problem, and solution is here.

2) OK:

Same triangle, same circle, but now we sum the square of the three distances ...????? and they sum to twice the square of a side of the equilateral triangle. That proof is here.

3) And now one with the circle on the inside. Again, from any point on the circle construct segments to the three vertices of the equilateral triangle. Again the sum of the squares is related to a side length, but I'll let you chase that down for yourself. Or you can go to the site here.

Addendum: John Golden sent a comment with a link to a GeoGebra sketch showing all three.

Recently among his posts have been a couple with a related theme, circles inscribed or circumscribed about an equilateral triangle. I'm listing these because they are each a wonderful relationship, and together give these otherwise somewhat mundane seeming triangles a luster students?teachers/others might miss.

I will post the problems, but not the proofs, which (if you can't/won't work them out yourself you can find at the links provided to Antonio's site.

So on we go...

1) draw a circle and inscribe an equilateral triangle. Now pick any point on the circumference and construct segments from this point to the three vertices. The sum of the lengths of the two shorter segments will equal the third. The problem, and solution is here.

2) OK:

Same triangle, same circle, but now we sum the square of the three distances ...????? and they sum to twice the square of a side of the equilateral triangle. That proof is here.

3) And now one with the circle on the inside. Again, from any point on the circle construct segments to the three vertices of the equilateral triangle. Again the sum of the squares is related to a side length, but I'll let you chase that down for yourself. Or you can go to the site here.

Addendum: John Golden sent a comment with a link to a GeoGebra sketch showing all three.

## Tuesday 14 January 2014

### Notes on the History of the Factorial

I recently came across a nice blog from Paul Hartzer who blogs at Hero's Garden about Kramp's work with factorials. It prompted me to share my more general notes on the early history of factorials. (This link seems to have gone dead. Anyone who knows about Paul please drop me a note about where he is posting now?)

I have a curiosity about the etymology and history of mathematical terms as well, so I have included some notes on the etymology of factorial at the bottom.

In his book on The Art of Computer Programming, Donald Knuth points to an example of the factorial (in particular 8!) in the Hebrew book of creation. NOTE (a comment corrects my poor writing here to point out that, "There is more than one volume, not just one book written by D. E. Knuth with the title "The Art of Computer Programming." There are four volumes. It is volume 2, subtitled "Seminumerical Algorithms", that mentions the Sefer Yetsirah ('Hebrew book of creation') as having an example of the factorial." Thank you)

The first use of a multiplication of long strings of successive digits for a specific problem may have been by Euler in solving the questions of derangements. "The Game of Recontre (coincidence), also called the game of treize (thirteen), involves shuffling 13 numbered cards, then dealing them one at a time, counting aloud to 13. If the nth card is dealt when the player says the number 'n,' the dealer wins (this is known in combinatorics as a derangement of 13 objects.). Euler calculated the probability that the dealer will win.

It should be noted that this problem was solved earlier, by P.R. de Montmort, in 1713, though his work was unknown to Euler."

In an article entitled, "Calcul de la probabilité dans le jeu de rencontre" published in 1753, Euler wrote.

which is translated by Richard J. Pulskamp as "The number of cases \(1^. 2^. 3^. 4 \dotsb m\) being put for brevity =M." Cajori points out that this was probably not intended to be a general notation, but a temporary expedient.

In 1772 A T Vandermonde used [P]

Vandermonde's symbol for [P]

The word factorial is reported to be the creation of Louis François Antoine Arbogast (1759-1803). The symbol now commonly used for factorial seems to have been created by Christian Kramp in 1808 according to a note I found in

Well after my first writing, Ben Gross of Ben Gross@bhgross144 posted an image of the cover page of Kramp's Élémens d'arithmétique universelle (1808), featuring the first use of n! to represent a factorial. I have captured these images from his twitter feed.

In his Dictionary of Curious and Interesting Numbers, David Wells tells the following story: "Augustus de Morgan ... was most upset when the " ! " made its way to England. He wrote: 'Among the worst of barbarisms is that of introducing symbols which are quite new in mathematical, but perfectly understood in common, language. Writers have borrowed from the Germans the abbreviation n! ... which gives their pages the appearance of expressing admiration that 2, 3, 4, etc should be found in mathematical results.'"

Another early symbol (shown below) was also used. Here is the description of its origin from the web page of Jeff Miller,

I later found a copy of the 1830 paper on Google Books, and here is the way Jarrett presented the notation:

The symbol persisted and both symbols were in use for some time. Cajori suggests that the Jarrett |

The image below is from the 1889 textbook,

A second image shows that the symbol was still in use even after the textbooks had adopted the "n!" symbol. This image is a note on the top a page on combinations in the 1922 text

I recently found even a later date of the use of the Jarrett symbol. In the Mathematics Teacher for February of 1946 the symbol is used in an article by C. V. Newsome and John F. Randolph in illustrating Newton's power series for Sin(x). The fact that it is done with no comment indicates it must have still been commonly used.

I also came across an Arabic use of a very similar symbol, that is apparently still current. A note from an AP calculus teacher in February of 2009 indicated that a transfer student from Egypt uses something like this symbol currently.

A variation of Vandermonde's [p/3]

I received a comment to this post from Maurizio Codogno who had an even later use of Jarrett's symbol for factorial. He writes, "I found the L notation for the factorial in the book The Math Entertainer,(by Philip Heafford) which is dated 1959 (I have the 1983 reprint) He even shared a digital copy from the book.

This may seem a big number of arrangements. It is the prod- uct of 6 x 5 x 4 x 3 x 2 x 1. Another way of writing this product is \( \lfloor6 \), or, as it is often printed, 6!. It is called factorial 6.

I am now wondering if the notation is still in use in some part of the globe. (Asked and answered, a note in the comments says "jarret's symbol is still used to this day in Arabic mathematics the L for factorial We never use the exclamation mark(!)")

A good approximation to n! for large values of n is given by

The Factorial can also be generalized to the real and complex numbers using the Gamma Function

There is also a subfactorial and symbol in math. I am still searching for links to early uses, variations, etc. What little I knew a few years ago (and today) is here. Would love to have your input.

Unfortunately the same symbol, !n, often used for the subfactorial, was applied in 1971 by D. Kurepa for the sum of factorials,\( !n=\sum _{k=0}^{n-1} k! \) so !5 would b 4! + 3! + 2! + 1! + 0! = 24 + 6 + 2 + 1 + 1=34 .

Amazingly these two seemingly unconnected sequences are related. For clarity if we call the subfactorial seqeunce S(n) and the factorial sum sequence F(n) then it can be shown that \( F(n) \equiv (-1)^{k-1} S(n-1)\) Mod n.

There are other variations on the factorial. The primorial is the product of all the primes less than or equal to n, and is usually expressed as n#, so 5# = 5*3*2. They are useful to prime hunters, and the term was created by the very successful prime finder, Harvey Dubner. I would love to have a source for it's use, or the creation of the symbol.

There is an alternating factorial which is the sum of the terms of a factorial sequence alternately added and subtracted. For example af(5) = 5!- 4! + 3! - 2! + 1!. The only symbol I have seen is af(n), but I think something like \( (n\pm)! \) would be somewhat elegant. Go forth and use it. Donald Knuth, are you reading this?

There is also a superfactorial, the product of the factorials from 1 to n, \(\prod\limits_{k=1}^n k! \). I have seen the symbol of a heart suggested, so 3 (heart-shape) would be 1!*2!*31.

There is even a hyperfactorial, although I have never seen it in use. H(n) = \(\prod\limits_{k=1}^n k^k \) These get big in a hurry. (If you have information on the origin and uses of any of these, please advise.)

The term factorial is drawn from the more common math (and English) term factor. The roots of both these words are in the word fact and its Latin root

Factors then became the parts of the whole, and a factory was where they were put together to make a final product. These words run over into the mathematical meanings. The factors are the numbers that are put together (by multiplication) to make the product. Because the product is made up by putting together parts, it is called a composite number.

The word "measure" has often been used in much the same way we now use the word factor. In his

Other English words from the "to do" meaning of fact include facility (the ability to do), faction (a group working to do the same thing), facilitate (make easy to do) and faculty.

I have a curiosity about the etymology and history of mathematical terms as well, so I have included some notes on the etymology of factorial at the bottom.

In his book on The Art of Computer Programming, Donald Knuth points to an example of the factorial (in particular 8!) in the Hebrew book of creation. NOTE (a comment corrects my poor writing here to point out that, "There is more than one volume, not just one book written by D. E. Knuth with the title "The Art of Computer Programming." There are four volumes. It is volume 2, subtitled "Seminumerical Algorithms", that mentions the Sefer Yetsirah ('Hebrew book of creation') as having an example of the factorial." Thank you)

The first use of a multiplication of long strings of successive digits for a specific problem may have been by Euler in solving the questions of derangements. "The Game of Recontre (coincidence), also called the game of treize (thirteen), involves shuffling 13 numbered cards, then dealing them one at a time, counting aloud to 13. If the nth card is dealt when the player says the number 'n,' the dealer wins (this is known in combinatorics as a derangement of 13 objects.). Euler calculated the probability that the dealer will win.

It should be noted that this problem was solved earlier, by P.R. de Montmort, in 1713, though his work was unknown to Euler."

In an article entitled, "Calcul de la probabilité dans le jeu de rencontre" published in 1753, Euler wrote.

which is translated by Richard J. Pulskamp as "The number of cases \(1^. 2^. 3^. 4 \dotsb m\) being put for brevity =M." Cajori points out that this was probably not intended to be a general notation, but a temporary expedient.

In 1772 A T Vandermonde used [P]

^{n}to represent the product of the n factors p(p-1)(p-2)... (p-n+1). With such a notation [P]

^{p}would represent what we would now write as p!, but I can imagine this becoming, over time, just [p] (De Morgan would do just such a thing in his 1838 essays on probability). Vandermonde seems to have been the first to consider [p]

^{0}(or 0!) and determined it was (as we now do) equal to one. Vandermonde's notation included a method for skipping numbers, so that [p/3]

^{n}would indicate p(p-3)(p-6)... (p-3(n-1)). It even allowed for negative exponents.

Vandermonde's symbol for [P]

^{n}would today represent what is generally called the "falling factorial." The common symbols seem to be [n]

_{k}or Donald Knuth's suggestion of \( n^{\underline{k}} \). Similar symbols exist for a "rising factorial", (n) (n+1) (n+2)...(n+k-1). Knuth's pleasing mnemonic version \( n^{\overline{k}} \) and (n)

_{k}which is common in working with hypergeometric series and is called the Pochammer symbol, although he never seemed to have used it for that, and used it for the combination of n things taken k at a time \( \binom{n}{k} \). I think either approach could be easily extended to using \ (n/s) as the base with the "s" representing the "skip rate". So (5/3)

_{4 }could represent the rising step factorial 5 * 8 * 11 * 14.

The word factorial is reported to be the creation of Louis François Antoine Arbogast (1759-1803). The symbol now commonly used for factorial seems to have been created by Christian Kramp in 1808 according to a note I found in

__Lectures on fundamental concepts of algebra and geometry__(1911), by John Wesley Young with a note on "The growth of algebraic symbolism" by Ulysses Grant Mitchell. It was in the Note by Mitchell (pg 239) that I found the credit for the symbol to Kramp. Kramp had previously used the word "facultes" for the process, but deferred in favor of Arbogast's term instead. Here is a translation from Jeff Miller's page, "I've named them facultes. Arbogast has proposed the denomination factorial, clearer and more French. I've recognised the advantage of this new term, and adopting its philosophy I congratulate myself of paying homage to the memory of my friend". Both Kramp and Arbogast were working with sequences of products. (Kramp's more general notation allowed for "the product of the factors of an arithmetic progression, that is,\(a(a+r)(a+2r)\dotsb(a+nr−r)\), I use the notation \(a^{n|r}\) is well described in the post mentioned above by Hartzer).

Well after my first writing, Ben Gross of Ben Gross@bhgross144 posted an image of the cover page of Kramp's Élémens d'arithmétique universelle (1808), featuring the first use of n! to represent a factorial. I have captured these images from his twitter feed.

Another early symbol (shown below) was also used. Here is the description of its origin from the web page of Jeff Miller,

An early factorial symbol, was suggested by Rev. Thomas Jarrett (1805-1882) in 1827. It occurs in a paper "On Algebraic Notation" that was printed in 1830 in the Transactions of the Cambridge Philosophical Society and it appears in 1831 in An Essay on Algebraic Development containing the Principal Expansions in Common Algebra, in the Differential and Integral Calculus and in the Calculus of Finite Differences (Cajori vol. 2, pages 69, 75).

I later found a copy of the 1830 paper on Google Books, and here is the way Jarrett presented the notation:

The symbol persisted and both symbols were in use for some time. Cajori suggests that the Jarrett |

__n__symbol was little used until picked up by I. Toddhunter in his texts around 1860, and it was the use of his texts in America that may have influenced its use in the USA where it was more popular than the current symbol until around WWI.

The image below is from the 1889 textbook,

__A College Algebra__by J.M. Taylor of Colgate.

A second image shows that the symbol was still in use even after the textbooks had adopted the "n!" symbol. This image is a note on the top a page on combinations in the 1922 text

__College Algebra__by Walter Burton Ford of the University of Michigan. The book uses the exclamation point notation, but the hand written reminder is in the notation of Jarrett (and perhaps the teacher of Ms. Mabel M Walker whose signature is in the front of the book).

I recently found even a later date of the use of the Jarrett symbol. In the Mathematics Teacher for February of 1946 the symbol is used in an article by C. V. Newsome and John F. Randolph in illustrating Newton's power series for Sin(x). The fact that it is done with no comment indicates it must have still been commonly used.

I also came across an Arabic use of a very similar symbol, that is apparently still current. A note from an AP calculus teacher in February of 2009 indicated that a transfer student from Egypt uses something like this symbol currently.

A variation of Vandermonde's [p/3]

^{n}which allow the symbol to be extended to the idea of multiplying every other number, or every third, etc. What is today called the double factorial, triple factorial etc. The earliest use I can find of either the "!!" notation or the term double factorial is by B. E. Meserve, in 1948 (Double Factorials, American Mathematical Monthly, 55 (1948)) His usage indicates he is using a well understood term, and symbol so I suspect there is earlier usage. For example the use of a double factorial, as in 7!! means multiply 7*5*3*1; and 7!!! would be 7*4*1 (every third multiple). This seems to be little or no improvement to my mind from the notation Vandermonde used for the same purpose. It is important not to confuse these symbols with (7!)! which is the factorial of 7! or 5040!.

I received a comment to this post from Maurizio Codogno who had an even later use of Jarrett's symbol for factorial. He writes, "I found the L notation for the factorial in the book The Math Entertainer,(by Philip Heafford) which is dated 1959 (I have the 1983 reprint) He even shared a digital copy from the book.

This may seem a big number of arrangements. It is the prod- uct of 6 x 5 x 4 x 3 x 2 x 1. Another way of writing this product is \( \lfloor6 \), or, as it is often printed, 6!. It is called factorial 6.

I am now wondering if the notation is still in use in some part of the globe. (Asked and answered, a note in the comments says "jarret's symbol is still used to this day in Arabic mathematics the L for factorial We never use the exclamation mark(!)")

A good approximation to n! for large values of n is given by

**Stirling's Formula**, which probably ought to be named for De Moivre. \( n! \approx \sqrt{2\pi n} (\frac{n}{e})^n\)

The Factorial can also be generalized to the real and complex numbers using the Gamma Function

There is also a subfactorial and symbol in math. I am still searching for links to early uses, variations, etc. What little I knew a few years ago (and today) is here. Would love to have your input.

Unfortunately the same symbol, !n, often used for the subfactorial, was applied in 1971 by D. Kurepa for the sum of factorials,\( !n=\sum _{k=0}^{n-1} k! \) so !5 would b 4! + 3! + 2! + 1! + 0! = 24 + 6 + 2 + 1 + 1=34 .

Amazingly these two seemingly unconnected sequences are related. For clarity if we call the subfactorial seqeunce S(n) and the factorial sum sequence F(n) then it can be shown that \( F(n) \equiv (-1)^{k-1} S(n-1)\) Mod n.

There are other variations on the factorial. The primorial is the product of all the primes less than or equal to n, and is usually expressed as n#, so 5# = 5*3*2. They are useful to prime hunters, and the term was created by the very successful prime finder, Harvey Dubner. I would love to have a source for it's use, or the creation of the symbol.

There is an alternating factorial which is the sum of the terms of a factorial sequence alternately added and subtracted. For example af(5) = 5!- 4! + 3! - 2! + 1!. The only symbol I have seen is af(n), but I think something like \( (n\pm)! \) would be somewhat elegant. Go forth and use it. Donald Knuth, are you reading this?

There is also a superfactorial, the product of the factorials from 1 to n, \(\prod\limits_{k=1}^n k! \). I have seen the symbol of a heart suggested, so 3 (heart-shape) would be 1!*2!*31.

There is even a hyperfactorial, although I have never seen it in use. H(n) = \(\prod\limits_{k=1}^n k^k \) These get big in a hurry. (If you have information on the origin and uses of any of these, please advise.)

The term factorial is drawn from the more common math (and English) term factor. The roots of both these words are in the word fact and its Latin root

*facere*, to do. To know the facts, is to know what has been done. The person who does something is then called the factor. In business a factor was once a common term for one who buys or sells for another. Today the word agent is more common. Colonial businesses often employed a person to do various menial tasks, as a factotum, literally one who does everything (today we might call them a "gopher"). Things that were necessary in order to "do something" became factors in the event, and today you may hear a coach say, "Defense was the most important factor in our victory."

Factors then became the parts of the whole, and a factory was where they were put together to make a final product. These words run over into the mathematical meanings. The factors are the numbers that are put together (by multiplication) to make the product. Because the product is made up by putting together parts, it is called a composite number.

The word "measure" has often been used in much the same way we now use the word factor. In his

__Universal Arithmetick__Newton distinguishes three kinds of numbers, "integer, fracted, and surd", and defines an integer as "what is measured by Unity." Frederick Emerson's

__North American Arithmetic__(1850)says "One number is said to MEASURE another, when it divides it without leaving any remainder." (pg 18) Later it states," A number which divides two or more numbers without a remainder is called their COMMON MEASURE." This is after the definition of factor on page 12, and immediately precedes "A square number is the product of two equal factors" on page 19.

Other English words from the "to do" meaning of fact include facility (the ability to do), faction (a group working to do the same thing), facilitate (make easy to do) and faculty.

## Wednesday 8 January 2014

### Oldest Multiplication Table Found?

"From an online article in Nature, Jan 2014:

From a few fragments out of a collection of 23-century-old bamboo strips, historians have pieced together what they say is the world's oldest example of a multiplication table in base 10.

(The Egyptian scrolls of 17th Century BC give a method equivalent to multiplication in base two ,although the scrolls are generally in base 60, see below)

Five years ago, Tsinghua University in Beijing received a donation of nearly 2,500 bamboo strips. Muddy, smelly and teeming with mould, the strips probably originated from the illegal excavation of a tomb, and the donor had purchased them at a Hong Kong market. Researchers at Tsinghua carbon-dated the materials to around 305 bc, during the Warring States period before the unification of China.

Each strip was about 7 to 12 millimetres wide and up to half a metre long, and had a vertical line of ancient Chinese calligraphy painted on it in black ink. Historians realized that the bamboo pieces constituted 65 ancient texts and recognized them to be among the most important artefacts from the period.

When the strips are arranged properly, says Feng, a matrix structure emerges. The top row and the rightmost column contain, arranged from right to left and from top to bottom respectively, the same 19 numbers: 0.5; the integers from 1 to 9; and multiples of 10 from 10 to 90.

The researchers suspect that officials used the multiplication table to calculate surface area of land, yields of crops and the amounts of taxes owed. “We can even use the matrix to do divisions and square roots,” says Feng. “But we can’t be sure that such complicated tasks were performed at the time.”

-------------------------

An older multiplication method (although not technically a multiplication table) is presented in ancient Egyptian scrolls)

In mathematics, ancient Egyptian multiplication (also known as Egyptian multiplication, Ethiopian multiplication, Russian multiplication, or peasant multiplication), one of two multiplication methods used by scribes, was a systematic method for multiplying two numbers that does not require the multiplication table, only the ability to multiply and divide by 2, and to add. It decomposes one of the multiplicands (generally the larger) into a sum of powers of two and creates a table of doublings of the second multiplicand. This method may be called mediation and duplation, where mediation means halving one number and duplation means doubling the other number. It is still used in some areas.

The second Egyptian multiplication and division technique was known from the hieratic Moscow and Rhind Mathematical Papyri written in the seventeenth century B.C. by the scribe Ahmes.

Although in ancient Egypt the concept of base 2 did not exist, the algorithm is essentially the same algorithm as long multiplication after the multiplier and multiplicand are converted to binary. The method as interpreted by conversion to binary is therefore still in wide use today as implemented by binary multiplier circuits in modern computer processors. *wik

This tablet, from about 2000 BC, was a school math book for teaching kids how to calculate inheritance. The problem asks how much each of seven boys would get when their father died, according to Babylonian law. Apparently the law said they should each get a different proportion, with the oldest getting the most and the younger kids less and less. Whoever did the math worked up from the bottom (which was not normal), and also made a mistake in his or her calculations!

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