Maya numerals were a vigesimal (base-twenty) numeral system used by the Pre-Columbian Maya civilization.
The numerals are made up of three symbols; zero (shell shape), one (a dot) and five (a bar). For example, nineteen (19) is written as four dots in a horizontal row above three horizontal lines stacked upon each other.
Numbers above 19
Numbers after 19 were written vertically in powers of twenty. For example, thirty-three would be written as one dot above three dots, which are in turn atop two lines. The first dot represents "one twenty" or "1×20", which is added to three dots and two bars, or thirteen. Therefore, (1×20) + 13 = 33. Upon reaching 20^2 or 400, another row is started. The number 429 would be written as one dot above one dot above four dots and a bar, or (1×20^2) + (1×20^1) + 9 = 429. The powers of twenty are numerals, just as the Hindu-Arabic numeral system uses powers of tens.
Other than the bar and dot notation, Maya numerals can be illustrated by face type glyphs or pictures. The face glyph for a number represents the deity associated with the number. These face number glyphs were rarely used, and are mostly seen only on some of the most elaborate monumental carving.
Addition and subtraction
Adding and subtracting numbers below 20 using Maya numerals is very simple.
Addition is performed by combining the numeric symbols at each level:
If five or more dots result from the combination, five dots are removed and replaced by a bar. If four or more bars result, four bars are removed and a dot is added to the next higher column.
Similarly with subtraction, remove the elements of the subtrahend symbol from the minuend symbol:
If there are not enough dots in a minuend position, a bar is replaced by five dots. If there are not enough bars, a dot is removed from the next higher minuend symbol in the column and four bars are added to the minuend symbol being worked on.
Note that this corresponds almost exactly to traditional addition and subtraction in the common base-10.
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