Roman Numerals - Reading and Writing Roman Numerals up to 1000

The Roman Numeral system uses seven basic symbols to represent numbers: $I = 1$, $V = 5$, $X = 10$, $L = 50$, $C = 100$, $D = 500$, and $M = 1000$. You can visualize these as a hierarchy of values where symbols are combined to represent any number up to $1000$.

Rule of Repetition: The symbols $I$, $X$, $C$, and $M$ can be repeated up to a maximum of three times in a row to represent addition (e.g., $III = 3$, $CCC = 300$). However, the symbols $V$, $L$, and $D$ are never repeated. Visually, if you see four identical symbols like $IIII$, it is incorrect; it should be written as $IV$.

Rule of Addition: If a symbol of smaller value is written to the right of a symbol of greater value, we add their values together. For example, in $LX$, the smaller $X$ (10) is to the right of $L$ (50), so $50 + 10 = 60$. This creates a descending visual pattern from largest to smallest value.

Rule of Subtraction: If a symbol of smaller value is written to the left of a symbol of greater value, we subtract the smaller value from the larger one. For example, $IV = 5 - 1 = 4$ and $CM = 1000 - 100 = 900$. Visually, this 'smaller-before-larger' pair stands out as a single unit within a longer numeral.

Subtraction Constraints: Only $I$, $X$, and $C$ can be used for subtraction. $I$ can only be subtracted from $V$ and $X$. $X$ can only be subtracted from $L$ and $C$. $C$ can only be subtracted from $D$ and $M$. Symbols $V$, $L$, and $D$ are never subtracted from any larger symbol.

Building Complex Numbers: To read or write large numbers, break the number into its place values (Hundreds, Tens, and Ones). For instance, $444$ is treated as $400 + 40 + 4$. Each part is converted separately ($CD + XL + IV$) and then joined to form $CDXLIV$.

No Zero: Unlike the Hindu-Arabic system, the Roman Numeral system has no symbol for zero ($0$). This means place values with a zero are simply skipped. For example, $505$ is $500 + 5$, which is $DV$.