The fifth rule - Addition of basic symbols in a Roman numeral
Numerals addition rule:
- A numeral placed immediately after another one of larger or equal value (next to the right of it), is added to the latter.
- This rule outweigh the third rule, that of subtraction, when writing Roman numerals.
- Only when a number can't be built by the addition rule, the subtraction rule applies.
- Also remember the rule no. 2, of repetition (numerals may not occur more than three times in a row in any numeral).
- Number two (2) is written using a single symbol listed under the first rule: I (1). Placing the I symbol after another I leads to: II (2);
- Number three (3) is also written by placing I after I (1) twice, so we get: III (3);
- Number six (6) is written by placing I (1) after V (5), so we get: VI (6);
- Number seven (7) is written by placing I (1) after V (5) twice, so we get: VII (7);
- Number eight (8) is written by placing I (1) after V (5) three times: VIII (8) - not IIX;
- Number eleven (11) is written by adding I (1) to X (10), by placing I (1) after X (10): 11 = 10 + 1 = X + I = XI;
- Number twenty (20) is written by placing X (10) after another X (10): 20 = 10 + 10 = X + X = XX;
- Number one hundred four (104) is written by placing IV (4) after C (100), to get 104 = 100 + 4 = C + IV = CIV.
Roman numerals reading rules, summary:
V. The fifth rule - numerals addition