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Topic: Why study Egyptian fraction math?
Replies: 20   Last Post: Nov 20, 2012 9:25 PM

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Milo Gardner

Posts: 1,105
Registered: 12/3/04
Re: Why study Egyptian fraction math?
Posted: Nov 4, 2012 7:51 AM
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A longer Planetmath paper makes the same points:

http://planetmath.org/encyclopedia/EgyptianFraction2.html

Prior to 2050 BCE Old Kingdom Egyptians rounded off top six-terms binary representations stated in 1/64 units. The Horus-Eye recorded rational numbers in the cursive pattern:

1 = 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64 + (1/64).

Note that a potential 7th term (1/64) was rounded-off and thrown way.

After 2050 BCE an exact numeration system discontinued the rounded-off Old Kingdom binary system. An exact hieratic weights and measures system reported rational numbers in 1/64 quotient and 1/320 remainder units whenever possible.

The new Middle Kingdom math system "healed" rounded off binary series by several finite methods. Two weights and measures finite systems can be reported by:

1. 1 hekat (a volume unit) used a unity (64/64)such that (32 + 16 + 8 + 4 + 2 + 1/64)hekat+ 5 ro

and (1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64)hekat + 5 ro

meant (64/64)/n = Q/64 + (5R/n)ro

Note that the hekat unity was generally divided by rational number n. To divide by 3 scribal long-hand would have written out

(64/64)/3 = 21/64 hekat + 5/192 = (16 + 4 + 1)/64 hekat + 5/3 ro =

(1/4 + 1/16 + 1/64)hekat + ( 1 + 2/3)ro

2. (100-hekat)/70 = (6400/64)/70 = 91/64 hekat + 30/4480 = (64 + 16 + 8+ 2 + 1)/64 hekat + 150/70 ro =

(1 + 1/4 + 1/8 + 1/32 + 1/64)hekat + (2 + 1/7)ro

meant (6400/64)/n = Q/64 + (5R/n)ro was applied for almost any hekat division problem.

The hieratic word ro meant 1/320 of a hekat in a grain weights and measures system. Note that 5 ro meant 5/320 = 1/64.

Generally, scribal shorthand recorded duplation aspects of mental calculations and fully recorded two-part hekat quotients and ro remainders.

At other times 2/64 was scaled to 10/320 such that (8 + 2)/320 = 1/40 + 2 ro

and so forth.



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