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Quinary (base-) is a numeral system with five as the base. This originates from the five fingers on either hand: the most primitive numeral system.
In the quinary place system, five numerals from 0 to 4, are used to represent any real number. According to this method, five is written as 10, twenty-five is written as 100 and sixty is written as 220.
In the twentieth century, only the East African Luo tribe of Kenya and the Yoruba of Nigeria were still using a base-five system. However, the base-ten (denary or decimal) system has prevailed in most areas and these tribes, like most previously quinary-counting cultures, have converted.
Henceforth, in this section, numbers are denary unless otherwise stated. For example, 5 means five, 10 means ten.
Usage
Roman numerals uses the quinary as the sub-base. 5 is written as V, 50 is L, 500 is D, but 25 (square of 5) is written as XXV, 125 (cube of 5) is written as CXXV. This is superimposed on a decimal base, which is sometimes referred to as the quinary-decimal system.
The Chinese version of the abacus uses a binary and a quinary system to simulate a decimal system.
A rarer variation is the quinary-vigesimal system, where quinary counting is used within cycles of 20 in a vigesimal system, such as the Maya numerals.
In the PC game Riven, by Cyan Worlds, the fictitious D'ni numerals play an important role for the solution of some puzzles. The system of the D'ni is actually a Quintevigesimal numerical system.
See also
"Quinary"