Example: What is the Hindu Arabic equivalent of XCII?
- D, L, or V may each only appear at most one time in the string
- M, C, X, or I may appear no more that three times consecutively in the string
- The following pairs of letters are invalid in all cases: IL, IC, ID, IM, XD, XM, VX, VL, VC, VD, VM, LC, LD, LM, DM.
- Once a letter has been subtracted from, neither it nor its "5 counterpart" may appear again in the string - so neither X nor V can follow IX, neither C nor L may follow XC, and neither M nor D may follow CM.
- Once a letter has been used as a subtraction modifier, it cannot appear again in the string - so C cannot follow CD or CM, X cannot follow XL or XC, and I cannot follow IV or IX.
- Once I, X, or C (or their "5-counterparts" V, L, and D) appears in a string, the I, X, or C cannot subsequently be used as subtraction modifiers - so IV or IX cannot follow I or V, XL or XC cannot follow X or L, and CD or CM cannot follow C or D.
X - 10
C - 100
II - 2
X before C implies 100 - 10
Hence 90 + 2
Example: What is the Hindu Arabic equivalent of VD?
Answer: Not valid
|Numeral ||Roman ||Numeral ||Roman |
|150 ||CL ||200 ||CC |
|300 ||CCC ||400 ||CD |
|600 ||DC ||700 ||DCC |
|800 ||DCCC ||900 ||CM |
|1000 ||M ||1600 ||MDC |
|1700 ||MDCC ||1900 ||MCM |
Directions: Write the corresponding Hindu Arabic numbers for the following. Also write at least 10 examples of your own.