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Roman numerals I V X L C D M
Hindu-Arabic numerals 1 5 10 50 100 500 1000

The Roman numeral system uses a combination of letters to represent numbers. It does

not use place value and has no symbol for zero. Numbers are formed by following the
four main rules:

Rule 1: If a symbol is repeated, its value is added as many times
Math Insight
as it occurs. Only I, X, C and M can

For example: (a) II = 1 + 1 = 2 (b) III = 1 + 1 + 1 = 3 be repeated three times
to write Roman numerals.
(c) XX = 10 + 10 = 20
Rule 2: If the smaller numeral is to the left of the bigger numeral, subtract it from the

bigger numeral.

For example: (a) IV = 5 – 1 = 4 (b) IX = 10 – 1 = 9 (c) XL = 50 – 10 = 40

Rule 3: If the smaller numeral is to the right of the bigger numeral, add the two numerals.

For example: (a) VI = 5 + 1 = 6 (b) XI = 10 + 1 = 11 (c) LX = 50 + 10 = 60
Rule 4: If the smaller numeral is between two numerals of greater value, subtract the

smaller numeral from the greater numeral to the right.

For example: (a) XIV = 10 + (5 – 1) = 10 + 4 = 14 (b) XIX = 10 + (10 – 1) = 10 + 9 = 19

Think Tank Logical Thinking
List 5 places where we use Roman numerals to write numbers.

The Roman numerals for the first 30 Hindu-Arabic numbers are shown below:

1 I 11 XI 21 XXI

2 II 12 XII 22 XXII

3 III 13 XIII 23 XXIII

4 IV 14 XIV 24 XXIV
5 V 15 XV 25 XXV

6 VI 16 XVI 26 XXVI

7 VII 17 XVII 27 XXVII

8 VIII 18 XVIII 28 XXVIII

9 IX 19 XIX 29 XXIX
10 X 20 XX 30 XXX

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