Roman Numerals

How to read and write roman numerals?

Hundreds of year ago, the Romans had a system of numbers which had only seven symbols. Each symbol had a different value and there was no symbol for 0.

The symbol of Roman Numerals and their values are:

Roman Numerals

Romans used different combinations of symbols to write numbers using adding and subtraction.
For reading and writing numbers upto 50 we need only the first 4 symbols.


Rules for the first five symbols

Multiplication Rule:

When a symbol is repeated in succession, we multiply the value of the numeral by the number of times it is repeated.
A symbol cannot be repeated more than three times in succession.

For example:

II = 1 × 2 = 2
XX = 10 × 2 = 20
XXX = 10 × 3 = 30
We cannot write 40 as XXXX.
The symbol cannot be repeated more than three times.

Addition Rule:

Writing a smaller number to the right of a larger number means the numbers have to be added.

For example:

VI = 5 + 1 = 6
XI = 10 + 1 = 11
XII = 10 + 1 + 1 = 12

Subtraction Rule:

Writing a smaller number to the left of a larger number means that the smaller number has to be subtracted from the larger number. The symbol 1 can be used for subtraction from V and X only. The symbol X can be subtracted only from L and C.

For example:

IV = 5 - 1 = 4
IX = 10 - 1 = 9
XL = 50 - 10 = 40
The symbol V cannot be repeated or subtracted.

We do not repeat V twice to get 10. We already have a symbol for 10. So VV for writing 10 is not correct.
We do not subtract 5 from any symbol. VX is not correct.

A list of Roman Numerals and their value are given below:

List of Roman Numerals Chart

Writing Numbers in Roman Numerals:

For example:

1. Write the Roman Numerals for 27. Break up the number into Tens and Ones.
27 = 20 + 7
Write the symbol for 20 (XX) and place the symbol for 7 (VII) after it.
27 convert roman numerals as XXVII

2. Write the Roman numeral number for 43.
43 = 40 + 3
Symbol for 40 XL
Symbol for 3 III
Roman Numerals for 43 is XLIII.

Reading Roman Numerals:

Look out for a subtraction operation. Do the subtraction before adding the numbers.

For example:

1. XXIV I = 1 V = 5 IV = 4
XX = 20
IV = 4
Hindu –Arabic numeral for XXIV is 24.

2. XIX IX = 9
Hindu –Arabic number for XIX = 19
In this example no subtraction is needed.
XXX = 30
II = 2
Hindu –Arabic number for XXXII = 32

Related Concept

Roman Numerals

Rules for Formation of Roman-numerals

Uses of Roman Numerals

4th Grade Math Activities

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