Last updated on May 26th, 2025
Roman numerals are a way of expressing numbers using symbols. I, V, X, L, C, D, and M are the symbols we use. Roman Numerals are used in royal titles, book names, sequences, and so on. Here we will discuss Roman Numerals, rules, and examples.
The royal titles, such as Henry I, Henry II, and so on. Have you noticed the names and wondered what these symbols (I and II) represented? Those are the Roman Numerals. Earlier people used fingers, sticks, bones, etc., to count. When life became complex, a standard form was required to count. Ancient Romans used the Roman Numeral system to count. I (1), V (5), X (10), L (50), C (100), D (500), and M (1000) are the symbols we use to count.
In Roman Numerals, we use CCCXXI to represent 321, where CCC is 300, XX is 20, and I is 1. Let’s learn more about Roman numerals and how we write them.
There are certain basic rules to write a number in Roman Numerals. In this section, let’s discuss some basic rules that need to be remembered when writing a number in Roman numerals.
Rule 1: Addition Method
The addition method is used when the smaller number is placed after the larger number. For example, XI → X + I → 10 + 1 = 11. For 321, it's CCC (300) + XX (20) + I (1) = 321.
Rule 2: Repetition Method
To write a large number, certain Roman Numerals can be repeated up to three times. For example, III → 3. For 321, CCC represents 300 (C repeated three times).
Rule 3: Subtraction Method
If a small number is followed by a large number in Roman Numerals, we subtract the smaller number from the large number. For example, IX → X - I → 10 - 1 = 9.
Rule 4: Limitation Rule
The symbols cannot be repeated more than three times, and some symbols like V, L, and D cannot be repeated. For example, we won't write VV for 10; instead, we use X.
Let’s now learn how to write 321 in Roman Numerals. Follow these methods to write the number in Roman Numerals.
In the expansion method, based on the place value, the number is broken down. In this section, we will learn how to write 321 in Roman numerals using the expansion method.
To write 321 in Roman Numerals, follow the steps:
Step 1: Break the number based on the place value: hundreds, tens, ones.
For 321, we write it as 300 + 20 + 1.
Step 2: Converting the number into Roman Numerals:
300 in Roman Numerals — CCC
20 in Roman Numerals — XX
1 in Roman Numerals — I
Step 3: Combine them together.
Therefore, 321 in Roman Numerals is CCC (300) + XX (20) + I (1) = CCCXXI.
When writing a large number into Roman Numerals, we group the number.
To write 321 in Roman Numerals, we group 321 as 300 + 20 + 1:
300 in Roman Numerals — CCC
20 in Roman Numerals — XX
1 in Roman Numerals — I
So, 321 is written as CCCXXI in Roman Numerals.
Students make mistakes when writing a number in Roman Numerals. To master Roman Numerals, we can learn a few common mistakes and ways to avoid them.
A historian discovers a scroll with the numbers CCCXXI and LXXI inscribed on it. What is the sum of these numbers in Roman numerals?
The sum of CCCXXI and LXXI is CCCXCII
CCCXXI = 321
LXXI = 71
321 + 71 = 392
392 in Roman numerals is CCCXCII.
A library has DCCCXLII ancient manuscripts, and they want to distribute them evenly among CXC students. How many manuscripts will each student receive?
Each student will receive IV manuscripts.
DCCCXLII = 842
CXC = 190
842 / 190 = 4
4 in Roman numerals is IV.
Find the product of XXI and XV in Roman numerals.
The product of XXI and XV is CCCXV
XXI = 21
XV = 15
21 × 15 = 315
315 in Roman numerals is CCCXV.
A collector has a collection of CCCXXI coins and sells XL coins. How many coins does the collector have left?
The collector has CCLXXXI coins left.
CCCXXI = 321
XL = 40
321 - 40 = 281
281 in Roman numerals is CCLXXXI.
Write the Roman numeral for the sum of CLX and CLXI using the expansion method.
The Roman numeral for CLX + CLXI is CCCXXI
Step 1: First convert the numbers CLX and CLXI into Roman numerals
CLX = 160
CLXI = 161
Add the numbers together: 160 + 161 = 321
Using the expansion method: 321 = 300 + 20 + 1 = CCCXXI
Hiralee Lalitkumar Makwana has almost two years of teaching experience. She is a number ninja as she loves numbers. Her interest in numbers can be seen in the way she cracks math puzzles and hidden patterns.
: She loves to read number jokes and games.