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Learn How to Use Roman Numerals

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Did you know that there are other different numbering systems? Did you know that our numbers come from the Arabic numbering system? Before the Arabs brought their numbering system (the one we use today) to Europe, in ancient Rome, the Romans invented a numbering system that we still use for some things. They are what we call Roman numerals.

How are Roman numerals used?

Roman numerals are formed from letters: X, L, I, C, D … Each letter has a numerical value:
roman numerals

To represent roman numerals, we must use these letters, combining and ordering them. You have to follow some rules:

  • The symbols are written and read from left to right, from highest to lowest value.

roman numeralsWhen a symbol is placed to the left of another with a higher value, it is subtracted.

roman numerals

  • Symbols representing a number containing a 5 (5, 50, 500, …) always add up and cannot be placed to the left of one with greater value.

roman numerals

  • At most, there are three consecutive repetitions of the same symbol.

roman numerals

  • A “subtracting” symbol cannot be “doubled.”

roman numerals

  • You can only use a subtracting symbol with the next two larger symbols.

The symbol I can only be subtracted from V and X.
The X symbol can only be subtracted from L and C.
The symbol C can only be subtracted from D and M.

As you can see through the explanations above, you need to know how to add and subtract in order to use roman numerals correctly!

What are the Roman numerals used for?

Today, we still use Roman numerals for some things. For example, in the following cases:

  • To name centuries:

    We are in the XXI (twenty-first) century

    The French Revolution occurred in the XVIII (eighteenth) century

    Michelangelo painted the Sistine Chapel in the XVI (sixteenth) century

  • To name the kings:

    Fernando II of Aragon married Isabella I of Castile.

    Felipe IV’s successor was Charles II.

  • To number the volumes of some books or movies:

    Yesterday I saw The Godfather II on TV.

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