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Showing posts with label Ancient Egyptian Multiplication Method Math Arithmetic Egypt. Show all posts
Showing posts with label Ancient Egyptian Multiplication Method Math Arithmetic Egypt. Show all posts

Monday, July 28, 2008

Ancient Egyptian Binary Multiplication

I will be showing the method used by the Ancient Egyptians as seen in the Text - " A History of Mathematics" by Jeff Suzuki. This is an excellent text and should be read by those with a great interest or love of mathematics and or history.
To do this multiplication we can use Suzuki's Pseudo-Hieratic notation. This involves writing a number such as 23 as 20,3. Another example would be writing 156 as 100,50,6.
So I will use the example Suzuki gives in the text. Namely, that of multiplying 13 by 27 or in Pseudo-Hieratic as 10,3 by 20,7. This may be considered a form of binary arithmetic because of the doubling. This method is also known as the Method of doubling and halving.
I will first show a step and then explain what is happening.


Step 1.

Col. 1 Col. 2
1 20,7

2 50,4

4 100, 8

8 200, 10, 6

Pick one of the numbers in this case 20,7 (27). Now, write a separate 1 term in a column to the left. Now double the row.That makes 1 go to 2 and 20,7 go to 50,4 (27*2 = 54).Doubling again makes turns the 2 into a 4 and 50,4 into 100,8 (54*2=108). Doubling once more 4*2 = 8 and108*2 = 216.The doubling does not go on forever of course. We do this until with some combination of the factors present in column 1 can make up the other original multiplying term. In this case 1,4, and 8 make up 10,3 (i.e 1+4+8 = 13).

Step 2.
Col. 1 Col. 2
\1 20,7
2 50,4
\4 100,8
\8 200,10,6

In step 2 we simply highlight the rows where the single digits in column 1 add up to 13. So Row's 1,3 and 4 have single digits 1,4,and 8 which sum to 10,3 (i.e 13).

Step 3.

20,7 + 100,8 + 200,10,6 = 300,50,1. ( 27 + 108 + 216 = 351).

Now, in step 3 we are looking at the rows of interest pointed out in Step 2. From there we add the terms in Column 2.