Pefsu problem (nonfiction)

In ancient Egyptian mathematics, a pefsu problem was a mathematical problem involving grain, bread, and beer.

Description

Pefsu is the conventional term for the strength of bread or beer made from a heqat (unit) of grain; it is often traslated as "the cooking" or "the cooking ratio (or number)."

A general mathematical expression is:

Pefsu = (no. of loaves of bread, or jugs of beer) / (no. of heqats of grain)

The higher the pefsu number, the weaker the bread or beer.

Example

Problem 8 in the Moscow Mathematical Papyrus translates as:

(1) Example of calculating 100 loaves of bread of pefsu

(2) If someone says to you: “You have 100 loaves of bread of pefsu

(3) to be exchanged for beer of pefsu

(4) like 1/2 1/4 malt-date beer"

(5) First calculate the grain required for the 100 loaves of the bread of pefsu

(6) The result is 5 heqat. Then reckon what you need for a des-jug of beer like the beer called 1/2 1/4 malt-date beer

(7) The result is 1/2 of the heqat measure needed for des-jug of beer made from Upper-Egyptian grain

(8) Calculate 1/2 of 5 heqat, the result will be 2 1/2

(9) Take this 2 1/a four times

(10) The result is 10. Then you say to him:

(11) Behold! The beer quantity is found to be correct"

Significance

Pefsu was a particularly useful number to know in a barter economy.

Nonfiction cross-reference

• Mathematics (nonfiction)

External links

• Ancient Egyptian mathematics @ Wikipedia
• Ancient Egyptian multiplication @ Wikipedia
• Egyptian algebra @ Wikipedia
• Moscow Mathematical Papyrus @ Wikipedia
• Ancient Egyptian Science: Ancient Egyptian Mathematics @ books.google.com
• Math Puzzles’ Oldest Ancestors Took Form on Egyptian Papyrus @ New York Times - In the Rhind papyrus, its scribe, known as Ahmes, introduces the roughly 85 problems by saying that he is presenting the "correct method of reckoning, for grasping the meaning of things and knowing everything that is, obscurities and all secrets."