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# Roman Numerals

Roman numerals are combinations of the seven letters

• I = 1
• V = 5
• X = 10
• L = 50
• C = 100
• D = 500
• M = 1000

Roman numbers are expressed by adding or subtracting combinations of the number values of the letters.

• smaller numbers before larger numbers are subtracted
• smaller number after larger numbers are added

Note that Roman numerals are without zero.

Large numbers are indicated with horizontal lines above them. With a horizontal line the number should be multiplied by 1000.

### Example - the Roman number 51

• LI => 50 + 1 = 51

### Example - the Roman number 9

• IX => -1 + 10 = 9

### Example - Years

• MCMLXXXII => 1000 + (-100 + 1000) + 50 + 10 + 10 + 10 + 1 + 1  = 1982
• MCMLXXVII => 1977

### Example - Large Roman Numbers

• V => 5 x 1000 = 5000

• 1 = I
• 2 = II
• 3 = III
• 4 = IV
• 5 = V
• 6 = VI
• 7 = VII
• 8 = VIII
• 9 = IX
• 10 = X
• 11 = XI
• 12 = XII
• 13 = XIII
• 14 = XIV
• 15 = XV
• 16 = XVI
• 17 = XVII
• 18 = XVIII
• 19 = XIX
• 20 = XX
• 30 = XXX
• 40 = XL
• 50 = L
• 60 = LX
• 70 = LXX
• 80 = LXXX
• 90 = XC
• 100 = C
• 150 = CL
• 200 = CC
• 300 = CCC
• 400 = CD
• 500 = D
• 600 = DC
• 700 = DCC
• 800 = DCCC
• 900 = CM
• 1000 = M
• 1600 = MDC
• 1700 = MDCC
• 1900 = MCM

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