Roman numerals are a numeral system that originated in ancient Rome and were used throughout the Roman Empire. They are still used today in certain contexts, such as for the numbering of chapters in books or the recording of dates on buildings. In this lesson, we will learn how to read and write Roman numerals.

## The Basics of Roman Numerals

Roman numerals use a combination of letters from the Latin alphabet to represent numbers. The basic symbols are:

- I = 1
- V = 5
- X = 10
- L = 50
- C = 100
- D = 500
- M = 1000

To form a number, these symbols are combined in various ways. The rules for forming numbers in Roman numerals are:

- Repeating a numeral up to three times represents addition of the number. For example, III is 3 (1+1+1) and XXX is 30 (10+10+10).
- If a smaller numeral is placed before a larger numeral, it represents subtraction of the smaller numeral from the larger numeral. For example, IV is 4 (5-1) and IX is 9 (10-1).
- If a smaller numeral is placed after a larger numeral, it represents addition of the smaller numeral. For example, VI is 6 (5+1) and XI is 11 (10+1).

## Reading and Writing Roman Numerals

To read Roman numerals, you simply add up the values of the symbols in the order they appear. For example, XVI is 16 (10+5+1) and MCMLXXXIV is 1984 (1000+100+1000+50+30+4).

To write a number in Roman numerals, you need to use the fewest possible symbols. There are also some conventions for representing certain numbers. For example, 4 is usually written as IV rather than IIII, and 9 is usually written as IX rather than VIIII.

## Practice Exercise

Now that you have learned about Roman numerals, let’s try a practice exercise.

Write the following numbers in Roman numerals:

- 25
- 77
- 149
- 666
- 1989

Answers:

- XXV
- LXXVII
- CXLIX
- DCLXVI
- MCMLXXXIX

Roman numerals are an ancient system of representing numbers that is still used today in certain contexts. By learning the basic symbols and rules for forming numbers in Roman numerals, you can read and write numbers in this system. Remember to use the fewest possible symbols and follow the conventions for representing certain numbers.