How to Convert Roman Numeral Subtractions

A simple method of subtracting Roman numerals without converting them back into Arabic numbers is to not use the subtraction rule. The subtraction rule is what makes it more appropriate to write "IV" instead of "IIII" to represent the number "4." To subtract Roman numerals, write them out without this rule, so that you may line up each group of letters.

Instructions

1. • 1

     Write out the Roman numerals that you wish to subtract. For instance, consider:

     LX

     - XIIII

   • 2

     Convert the Roman numerals to the format of the lowest number in the equation:

     XXXXX V IIIII

     - X IIII

   • 3

     Subtract each group of letters as you would normally:

     IIIII - IIII = I

     V - 0 = V

     XXXXX - X = XXXX

   • 4

     Resume the subtraction rule to properly format the answer:

     XXXXVI = XLVI