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

• Egyptian algebra @ Wikipedia
• Moscow Mathematical Papyrus @ Wikipedia
• Ancient Egyptian Science: Ancient Egyptian Mathematics @ books.google.com