1. A letter repeats its value that many times (XXX = 30, CC = 200, etc.). A letter can only be repeated three times.
2. If one or more letters are placed after another letter of greater value, add that amount. VI = 6 (5 + 1 = 6)LXX = 70 (50 + 10 + 10 = 70)MCC = 1200 (1000 + 100 + 100 = 1200)
3. If a letter is placed before another letter of greater value, subtract that amount. IV = 4 (5 – 1 = 4)XC = 90 (100 – 10 = 90)CM = 900 (1000 – 100 = 900)