The
symbols are normally arranged in descending order and the values are simply
added together.
Where a
symbol of lesser value comes before a symbol of greater value then the
lesser value is subtracted.
For example
IV
acutually means 5 - 1 = 4 and
CMII
means 1000 - 100 + 1 + 1 = 902
Only
C,
X
and I
can be subtracted and only one smaller symbol can be used.
The symbol used
for subtraction must not be less than a tenth of the value of the
number it precedes.
So something
like IIX
or LM
is NOT allowed.
(IIX uses two smaller
numbers (II) before the larger one (X) and L(50) is less than one
tenth the size of M(1000))