Let us gain knowledge of Roman numerals.
In ancient times, many civilizations used different number systems. Mayans, Egyptians, Indians, Romans, etc had their own number system.
The numbers from 09 were first invented in India. Later, the Arabs were greatly influenced by this number system and started using it. The Arabs also introduced this number system in Europe. Now, this number system is used worldwide and is called the HinduArabic number system.
Just like this, the Romans used their own number system for counting. Today, we use these roman numerals in clocks and watches. Ancient Romans used “7” letters to write numbers.
These letters were I, V, X, L, C, D, and M. The combination of these numbers makes the roman numerals. Where
I  V  X  L  C  D  M 
1  5  10  50  100  500  1000 
The roman numerals from 1100 are –
It is to be noted, there is no representation for “0(zero)” in the roman numerals.
Rules for Roman Number System
 Rules for repetition

 If a symbol is repeated, its value is added as many times as it occurs. For e.g.
X = 10
Then, XX= 10+10 = 20
And XXX = 10+10+10 =30
Let us take another example,
M = 1000
and MM = 1000+1000 =2000
also, MMM =1000+1000+1000 = 3000  A symbol is never repeated more than three times. for example,
 If a symbol is repeated, its value is added as many times as it occurs. For e.g.


 I = 1

 II = 2



 III=3


 But IIII ≠ 4 Thus it is written as IV = 4.

 The symbol V, L and D are never repeated.
For example,
V = 5
but VV ≠ 10
and X = 10

For addition
 When the symbol of smaller value is written to the right of greater symbol value, its value gets added to the value of greater symbol. For e.g.
VII = 5 + 2
and XI = 10 + 1 = 11
LXVI = 50 + 10 + 6 = 66
For subtraction
If a symbol of a smaller value is written to the left of a symbol of greater value, its value is subtracted from the value of the greater symbol.
e.g
IX = 10 – 1 = 9
XL = 50 10 = 40
The symbols V, L and D are never written to the left of a symbol of greater value. i.e. V, L and D are never subtracted.
Also, The symbol I can be subtracted from V and X only. And X can be subtracted from L, M and C only.
Let us solve some questions.
(i) 121
(iii) 303
(i) CMIV
(iii) CCXLV