RomanNumerals 2002-08-20 01:31:34 2004-04-02 09:18:22 Definition % this is the default PlanetMath preamble. as your knowledge % of TeX increases, you will probably want to edit this, but % it should be fine as is for beginners. % almost certainly you want these \usepackage{amssymb} \usepackage{amsmath} \usepackage{amsfonts} % used for TeXing text within eps files %\usepackage{psfrag} % need this for including graphics (\includegraphics) %\usepackage{graphicx} % for neatly defining theorems and propositions %\usepackage{amsthm} % making logically defined graphics %\usepackage{xypic} % there are many more packages, add them here as you need them % define commands here %\PMlinkescapeword{theory} \emph{Roman numerals} are a method of writing numbers employed primarily by the ancient Romans. It place of digits, the Romans used letters to represent the numbers central to the system: \begin{tabular}{cc} $I$&$1$\\ $V$&$5$\\ $X$&$10$\\ $L$&$50$\\ $C$&$100$\\ $D$&$500$\\ $M$&$1000$ \end{tabular} Larger numbers can be made by writing a bar over the letter, which means one thousand times as much. For instance $\overline{V}$ is $5000$. Other numbers were written by putting letters together. For instance $II$ means $2$. Larger letters go on the left, so $LII$ is $52$, but $IIL$ is not a valid Roman numeral. One additional rule allows a letter to the left of a larger letter to signify subtracting the smaller from the larger. For instance $IV$ is $4$. This can only be done once; $3$ is written $III$, not $IIV$. Also, it is generally required that the smaller letter be the one immediately smaller than the larger, so $1999$ is usually written $MCMXCIX$, not $MIM$. It is worth noting that today it is usually considered incorrect to repeat a letter four times, so $IV$ is preferred to $IIII$. However many older monuments do not use the subtraction rule at all, so $44$ was written $XXXXIIII$ instead of the now preferable $XLIV$.