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Roman Numerals

by Ron Kurtus (3 November 2017)

Roman numerals consist of a numbering system from the ancient Roman Empire that uses certain letters of the alphabet and their combinations to indicate numbers. The system is based on seven major symbols.

When counting with Roman numerals is done by adding a symbol to the previous combination, except for certain numbers before an major symbol.

Problems with using Roman numerals caused the change to our present Hindu-Arabic symbols. However, Roman numerals are still used in special cases.

Questions you may have include:

This lesson will answer those questions.



Major roman numeral symbols

Major Roman numeral symbols that make up the other numbers are I, V, X, L, C, D, and M. Their values are:

Symbol I V X L C D M
Value 1 5 10 50 100 500 1,000

Counting

Designating other numbers is done by adding a symbol to the previous combination. Exceptions are for the number preceding a major symbol, such as for 4, which precedes 5. In those cases, a symbol is placed in front. A list of Roman numerals from 1 to 20 gives you an idea of the sequence:

I, II, III, IV, V, VI, VII, VIII, IX, X,
XI, XII, XIII, XIV, XV, XVI, XVII, XVIII, XIX, XX
and so on.

Note that 4 is IV, 9 is IX, 14 is XIV, and 19 is XIX.

Also, 40 is not XXXX, rather it is 10 less than 50 or XL. Likewise, 400 is CD.

Strange combinations

Strange combinations include VX, which is five less than ten. Instead, it just should be V. Another situation is DM, which is 500 less than 1000. Instead, it should just be D. (Is this confusing or what?)

Problems with using Roman numerals

When you add two Roman numerals, you may often have to do some conversions. For example, adding 17 and 19, you get XVII + XIX = XIXVII, which would have to be rearranged and converted into IXXII = XXVI. Certainly, that is awkward.

Multiplying and dividing with Roman numerals is even more difficult. (I don't know how people in those days handled such calculations.)

This was a major reason for moving to the Hindu-Arabic number system that we use today.

Still used in some places

However, Roman numerals are still used in certain situations, such as:

Apparently, the reason to use the Roman numerals is to appear unique.

Summary

Roman numerals is a numbering system that uses certain letters of the alphabet and their combinations to indicate numbers. The system is based on seven major symbols, and counting is done by adding a symbol to the previous combination, except for certain numbers before an major symbol.

Problems with using Roman numerals caused the change to our present Hindu-Arabic symbols. However, Roman numerals are still used in special cases.


"When in Rome, do as the Romans do"


Resources and references

Ron Kurtus' Credentials

Websites

Roman Numerals - MathisFun.com

Roman numerals - Wikipedia

Convert Arabic to Roman Numerals - CalculateMe.com

Arithmetic Resources

Books

Top-rated books on Arithmetic


Questions and comments

Do you have any questions, comments, or opinions on this subject? If so, send an email with your feedback. I will try to get back to you as soon as possible.


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