Roman Numerals
Roman numerals are a combinations of seven letters.
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
Example  some common Roman numbers
 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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