The fourth rule - additive notation of the Roman numerals

The additive notation of the Roman numerals:

  • A numeral placed immediately after another one of a larger or equal value (next to the right of it), is added to the latter. This is called additive notation.
  • The fourth rule takes precedence over the third rule, that of the subtractive notation, when writing Roman numerals.
  • Only if a number can no longer be constructed using the additive notation, taking into account rule no. 2, that of the repetition (the symbols may not be repeated more than three times in a row), only then the subtractive notation is applied.

Addition. Learn by example how to add Roman numerals the right way, like the Romans calculated, steps, explanations

Example:

  • Number 2 is written by placing the I (1) symbol after another I (1): 2 = 1 + 1 = I + I = II;
  • Number 3 is also written by placing I (1) after I (1) twice: 3 = 1 + 1 + 1 = I + I + I = III;
  • Instead, number 4 is NOT to be written by placing I (1) after I (1) 3 times: 4 = 1 + 1 + 1 + 1 = I + I + I + I = IIII because it would contradict rule no. 2 of the repetition of the numerals (a symbol can be repeated up to 3 times in a row), so 4 is constructed using the subtractive notation rule: 4 = 5 - 1 = V - I = IV;
  • Number 6 is written by placing I (1) after V (5): 6 = 5 + 1 = V + I = VI;
  • Number 7 is written by placing I (1) after V (5) twice: 7 = 5 + 1 + 1 = V + I + I = VII;
  • Number 8 is written by placing I (1) after V (5) three times: 8 = 5 + 1 + 1 + 1 = V + I + I + I = VIII - not IIX;
  • Instead, number 9 is NOT to be written by placing I (1) after V (5) four times: 9 = 5 + 1 + 1 + 1 + 1 = V + I + I + I + I = VIIII because it would contradict rule no. 2 of the repetition of the numerals (a symbol can be repeated up to 3 times in a row), so 9 is constructed using the subtractive notation: 9 = 10 - 1 = X - I = IX;
  • Number 11 is written by adding I (1) to X (10), by placing I (1) after X (10): 11 = 10 + 1 = X + I = XI;
  • Number 20 is written by placing X (10) after another X (10): 20 = 10 + 10 = X + X = XX;
  • Number 104 is written by placing IV (4) after C (100) to get 104 = 100 + 4 = C + IV = CIV.

Addition. Learn by example how to add Roman numerals the right way, like the Romans calculated, steps, explanations

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 - subtractive notation of the Roman numerals

IV. The fourth rule - additive notation of the Roman numerals


How to convert Arabic numbers to Roman numerals: breaking down into place value subgroups

Examples of converting Arabic numbers to Roman numerals


Roman numerals from 1 to 100

Roman numerals from 1 to 1000

Mathematical operations with Roman numerals:

I. Addition. Learn by example how to add Roman numerals the right way, like the Romans calculated, steps, explanations

II. Subtraction. Learn by example how to subtract Roman numerals the right way, like the Romans calculated, steps, explanations

III. Addition and subtraction. Learn by example how to add and subtract Roman numerals the right way, like the Romans calculated, steps, explanations