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A.4 Read and write Roman numerals

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What are Roman numerals?

Roman numerals are a number system that uses letters from the Latin alphabet to represent values. Each letter stands for a specific number, and together they show quantities just like our regular numbers (0–9).

Examples:
  • I = 1
  • V = 5
  • X = 10
  • L = 50
  • C = 100
  • D = 500
  • M = 1,000
Note

Roman numerals do not use a symbol for zero. They were used long before our modern number system was developed.

How do Roman numerals work?

Roman numerals are formed by combining letters and adding or subtracting their values. When a smaller numeral appears before a larger one, you subtract. When it appears after, you add.

Examples:
  • VI = 5 + 1 = 6
  • IX = 10 − 1 = 9
  • XV = 10 + 5 = 15
Note

Always write numerals using the largest values first, except when a smaller numeral comes before a larger one to show subtraction.

Reading and writing larger Roman numerals

Roman numerals can be used to show numbers up to thousands by repeating or combining symbols. The same rules of addition and subtraction apply.

Examples:
  • LXX = 50 + 10 + 10 = 70
  • CXL = 100 − 10 + 50 = 140
  • CCLXV = 100 + 100 + 50 + 10 + 5 = 265
  • CM = 1,000 − 100 = 900
Note

The same letter cannot be repeated more than three times in a row. For example, write 40 as XL (50 − 10), not XXXX.

Roman numerals in everyday life

Even though we use regular numbers every day, Roman numerals are still seen in books, clocks, movie titles, and important events like the Olympics or the Super Bowl.

Examples:
  • Book chapters: Chapter IV (Chapter 4)
  • Clock faces: The number 9 is written as IX
  • Super Bowl LVIII = 58
Note

Understanding Roman numerals helps you read dates, labels, and symbols that appear in both history and modern life.

Tips for remembering Roman numerals

Learn the basic symbols first, then practice reading and writing them in order. Use patterns to help remember the values.

Helpful Patterns:
  • I = 1, II = 2, III = 3 (add one each time)
  • IV = 4 (5 − 1)
  • IX = 9 (10 − 1)
  • XL = 40 (50 − 10)
Note

Practice writing dates or numbers you see around you using Roman numerals. The more you use them, the easier they become to read.