Roman numerals originated in Ancient Rome and were the primary system until the Late Middle Ages. Although there are some variants of the symbols used for this numbering system, in the pharmacy there are 7 symbols to which you will see most often: I, V, X, L, C, D, M.
When deciphering Roman numerals there are 4 essential rules to remember:
- When one or more numerals are placed after a numeral of greater value you add. Example – MXV (1,000 + 10 + 5 = 1015)
- When a numeral is placed before a numeral of greater value you subtract. Example – IV = 4, IX = 9
- A repeated numeral (never more than 3 times) is added that many times. Example – CC = 200
- Always look for and perform subtraction first in long strings of numerals. Example – LXIV= LX + (IV)
Chart of Common Roman numerals:
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