How to read and write Roman numerals?

How to read and write Roman numerals?

The roman numerals is a system of symbols used to express quantities and values. The system uses seven letters of the Roman alphabet in capital letter, each of which represents a value and whose combination allows to build different numbers.

It is an alternative to the Arabic numeral system, which is more commonly used throughout the world.

What are Roman numerals used for?

Although for the basic functions of mathematics they are expressed with Arabic numbers, the Roman numeration system was not completely obsolete; is used for:

What are the Roman numerals?

Rules for reading and writing Roman numerals

To use this system, in addition to symbols, it is necessary to know the rules with which they are combined to express other values.

Rule # 1

• The letter I is equal to 1, but if it is located to the left of the letters V (5) or X (10), that value is discounted, and these letters together make up a new figure. For instance:

IV = 4 (because 5 minus 1 equals 4)
IX = 9 (because 10 minus 1 equals 9)

• On the contrary, if the letter I is placed to the right of V or X, this value is added and in each case composes a new figure. For instance:

SAW = 6 (because 5 plus 1 equals 6)
XI = 11 (because 10 plus 1 equals 11)

Rule # 2

• The letter X equals 10, but, located to the left of the letters L (50) and C (100), indicates that this value must be subtracted and a new figure is composed in each case. For instance:

XL = 40
XC = 90

• On the other hand, if the letter X is placed to the right of L or C, this indicates that its value is added to form new figures. For instance:

LX = 60
CX = 110

Rule # 3

• The letter C equals 100, but, if placed to the left of the letters D (500) or M (1000) this indicates that this value is subtracted to form a new figure. For instance:

CD = 400
CM = 900

• In turn, if the letter C is placed to the right of the letters D or M, this value is added to form new figures. For instance:

DC = 600
MC = 1100

(!) It should also be remembered that:

• It is not possible to put more than one letter in the left position, to subtract that value.
• In the position on the right, a maximum of three identical letters can be placed simultaneously, to form new figures by adding. For instance:

XIII = 13
DCCC = 800

• The letters D, L and V They cannot be subtracted or added, and therefore cannot be placed to the left of another letter or repeated.
• The letters M, C, X, I they can be deducted or added, therefore they can be placed on the left up to once (following the rules previously seen) or placed up to three times in a row on the right side.
• In numbers greater than 3999 (MMMCMXCIX), the numerical representation changes: a bar is added above the value that indicates that it is multiplied by a thousand. For instance:

__
IV = 4000

• If two bars are added above the letters, this indicates that the value is multiplied by one million.

Examples of Roman numerals and their Arabic equivalence

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