Roman Numerals:

An Ancient Number System

Roman numerals are an ancient number system that uses specific letters of the alphabet to represent fixed positive numbers. This system is still used in many places today, such as in clock faces, book chapter titles, and movie sequels. Here is a basic guide to understanding and using Roman numerals.

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Basic Roman Numerals

The Roman numerals for the numbers 1 through 10 are as follows:

• I = 1
• II = 2
• III = 3
• IV = 4
• V = 5
• VI = 6
• VII = 7
• VIII = 8
• IX = 9
• X = 10

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Key Roman Numerals and Their Values

Beyond the numbers 1 to 10, here are some additional key Roman numerals:

• L = 50
• C = 100
• D = 500
• M = 1,000

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Forming Numbers with Roman Numerals

To form numbers with Roman numerals, combine these letters. Here are some rules and examples:

Adding Values

If a smaller numeral comes before a larger one, subtract the smaller value. If a smaller numeral comes after a larger one, add the smaller value.

Examples

• II = 1 + 1 = 2
• III = 1 + 1 + 1 = 3
• VI = 5 + 1 = 6
• VII = 5 + 1 + 1 = 7
• VIII = 5 + 1 + 1 + 1 = 8
• XII = 10 + 1 + 1 = 12
• XXVII = 10 + 10 + 5 + 1 + 1 = 27

Subtracting Values

• IV = 5 – 1 = 4
• IX = 10 – 1 = 9
• XL = 50 – 10 = 40
• XC = 100 – 10 = 90
• CD = 500 – 100 = 400
• CM = 1,000 – 100 = 900

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Combining Numerals for Larger Numbers

Combine these numerals to form larger numbers:

• XIII = 10 + 3 = 13
• XXIV = 10 + 10 + 4 = 24
• XLII = 40 + 2 = 42
• LXXXIX = 80 + 9 = 89
• XCVI = 90 + 6 = 96
• CXXIII = 100 + 20 + 3 = 123
• CLV = 100 + 50 + 5 = 155
• CDXLIV = 400 + 40 + 4 = 444
• DCCCXC = 800 + 90 = 890
• CMXCIX = 900 + 90 + 9 = 999
• MCMXC = 1,000 + 900 + 90 = 1,990

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Summary

Roman numerals are a fascinating system of numbering that dates back to ancient Rome. By understanding the values of individual Roman numerals and how to combine them, you can read and write numbers in this timeless format.