# Roman Numerals: The Rules

There are three basic rules to remember:

1. No symbol is used more than 3 times in a row:

2. If a symbol appears after a larger or equal symbol, it is added to it:

Note: This works in all cases except VV. The symbol X is used to represent the number 10 therefore VV is not needed.

3. When the left-hand symbols are smaller than the right, subtract them from the right-hand symbol:

Note:
We can only subtract one character from another, so IIX would not be one and one from ten = 8.
Instead, to get 8 we would have to use VIII meaning 5+1+1+1=8.

We can start counting and apply the rules we learnt using the sentence:

'I Value Xylophones Like Cows Do Milk'.
I=1,  V=5,  X=10,  L=50,  C=100,  D=500,  M=1000

1. I

2. II

3. III

4. cancel(IIII) – No symbol is used more than 3 times.
IV (1 from 5 = 4) – when left is small and right is bigger, subtract left from right-hand figure.

5. V

6. VI (5 add 1 = 6) – If a symbol appears after a larger or equal figure it is added.

7. VII (5 add 1 add 1 = 7) – If a symbol appears after a larger or equal figure it is added.

8. VIII (5 add 1 add 1 add 1 = 8) – If a symbol appears after a larger or equal figure it is added.

9. cancel(VIIII) – No symbol is used more than 3 times.
IX (1 from 10 = 9) – when left is small and right is bigger, subtract left from right-hand figure.

10. X

This pattern continues for every number.