The third rule - Subtraction of basic symbols in subtractive notation of a Roman numeral (placing lower value symbols in front of larger value ones)

Numerals subtraction rule in subtractive notation:

  • A numeral of a lesser value placed in front (next to the left) of a larger value numeral is subtracted from the larger one. This is called subtractive notation.
  • Only these symbols are allowed to be used in subtractive notation: I (1), X (10), C (100), M (1,000), (X) (10,000), (C) (100,000), (M) (1,000,000).
  • Numerals V (5), L (50), D (500), (V) (5,000), (L) (50,000), (D) (500,000) are NOT allowed to be used in subtractive notation.
  • Important: Please also see the next rule, no. 4.

Examples:

  • Number four (4) is written using two important symbols listed under the first rule, I (1) and V (5): subtracting I from V, by placing I next to the left of the V symbol. We thus obtain: 4 = 5 - 1 = V - I = IV.
  • Number nine (9) is written using two important symbols listed under the first rule, I (1) and X (10): subtracting I from X by placing I next to the left of X symbol. We thus obtain: 9 = 10 - 1 = X - I = IX.

Roman numerals reading rules, summary:

I. The first rule - Roman numerals set of basic symbols

II. The second rule - numerals repetition

III. The third rule - numerals subtraction (subtractive notation)

IV. The fourth rule - what numerals are allowed to be subtracted from larger value numerals in the subtractive notation

V. The fifth rule - numerals addition (additive notation)

VI. The sixth rule - Arabic numbers decomposing (breaking down) into place value subgroups, in expanded notation, before converting to Roman numerals


Examples of converting Arabic numbers into Roman numerals


Roman numerals from 1 to 100

Roman numerals from 1 to 1000