Page 23 - ICSE Math 5

Roman Numeralsoman Numerals
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Learning Outcomes

Students will be able to learn:
 about Roman numeral system.
 the rules for writing Hindu-Arabic numbers using Roman numerals and vise versa.
 to add and subtract Roman numerals.

The most commonly used numeral system is the Hindu-Arabic numeral system which uses the
numerals (numbers) 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9. The other numeral system used is the Roman
numeral system which represents numerals using the symbols I, V, X, L, C, D and M. Let’s learn
more about Roman numerals in this chapter.
Roman Numeral System

The Roman numeral system is one of the oldest numeral system developed by the Romans.
This numeral system is based on seven distinct symbols. Each symbol has a different value. The
Roman numeral system uses either one of the symbols or combinations of symbols to write
numbers in the Hindu-Arabic numeral system. However, this system does not have any symbol
to represent zero.
The seven symbols of Roman numerals represent the following numbers of the Hindu-Arabic
numeral system.

Symbol in the Roman Numeral System I V X L C D M
Value in the Hindu-Arabic Numeral System 1 5 10 50 100 500 1,000

Rules for Writing Hindu-Arabic Numbers Using Roman Numerals

There are some rules for writing numbers using Roman numerals. They are as follows.
Rule 1: A Roman number can be repeated only thrice in a row. When it is repeated, its value
gets added to obtain a final value.

Examples:

II = 1 + 1 = 2 III = 1 + 1 + 1 = 3
XX = 10 + 10 = 20 XXX = 10 + 10 + 10 = 30
CC = 100 + 100 = 200 CCC = 100 + 100 + 100 = 300

MM = 1,000 + 1,000 = 2,000 MMM = 1,000 + 1,000 + 1,000 = 3,000

Exception to the rule

Only I, X, C and M can be repeated in the formation of numbers while V, L and D cannot be
repeated.
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