The ancient Romans gave us this numbering system. We still use it today for dates on buildings, to number the front matter in books, and for decorative purposes.
One | I | Eleven | XI | Thirty | XXX |
Two | II | Twelve | XII | Forty | XL |
Three | III | Thirteen | XIII | Fifty | L |
Four | IV | Fourteen | XIV | Sixty | LX |
Five | V | Fifteen | XV | Seventy | LXX |
Six | VI | Sixteen | XVI | Eighty | LXXX |
Seven | VII | Seventeen | XVII | Ninety | XC |
Eight | VIII | Eighteen | XVIII | One hundred | C |
Nine | IX | Nineteen | XIX | Five hundred | D |
Ten | X | Twenty | XX | One thousand | M |