Page 24 - ICSE Math 4

Roman Numeralsoman Numerals
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Learning Outcomes

Students will be able to learn:
 Roman numeral symbols I, V, L, C, D, and M.
 how to read Roman numerals.
 how to write Roman numerals for Hindu-Arabic numerals and vise versa.

The Roman numeral system was developed by the Top Tip
Romans thousands of years ago. It is based on seven
The Roman numeral
le ers of the alphabet where the le ers are used as system does not have

symbols. All the numbers are wri en using either one a symbol to represent
of the le ers or combina ons of le ers. zero.

Symbols of Roman Numerals

The seven symbols used in the Roman numeral system and their corresponding values in
Hindu-Arabic numeral system are given in the following table.

Symbol I V X L C D M

Value 1 5 10 50 100 500 1000

Reading Roman Numerals

We have seen that there are symbols for numbers 1, 5, 10, 50, 100, 500 and 1,000. To build

all the other numbers, we combine the above le ers according to the rules given below.
Rule 1: When a symbol is repeated, it means the value of Remember
each symbol is added that many mes. The sum is equal
to the number formed. However, a symbol cannot be Only the letters I, X,
C and M are repeated.
repeated more than 3 mes.
The letters V, L and D
Examples: II = 1 + 1 = 2, III = 1 + 1 + 1 = 3, XX = 10 + 10 = 20, are never repeated.
XXX = 10 + 10 + 10 = 30

Rule 2: When a smaller symbol or symbols are wri en a er a larger one, then their values
are added to get the number.

Examples: XV = 10 + 5 = 15, VIII = 5 + 1 + 1 + 1 = 8, XIII = 10 + 1 + 1 + 1 = 13
Rule 3: When a smaller symbol is wri en before a larger one, then the value of the smaller
symbol is subtracted from the value of the larger symbol.

Examples: IV = 5 – 1 = 4, IX = 10 – 1 = 9

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