Last updated on May 26th, 2025
Roman numerals are a way of expressing numbers using symbols. The symbols I, V, X, L, C, D, and M are used. Roman numerals are found in royal titles, book names, sequences, and more. Here, we will discuss Roman numerals, their rules, and examples.
Royal titles, such as Henry I, Henry II, and so forth, often use Roman numerals. Have you ever noticed these symbols and wondered what they represent? Those are Roman numerals. In ancient times, people used fingers, sticks, bones, etc., to count. As life became more complex, a standard form was required for counting. Ancient Romans developed the Roman numeral system for this purpose. The symbols I (1), V (5), X (10), L (50), C (100), D (500), and M (1000) are used in this system.
In Roman numerals, we use XLV to represent 45. Here, XL is 40 and V is 5. 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, VI (V + I) is 5 + 1 = 6.
Rule 2: Repetition Method
To write a large number, certain Roman numerals can be repeated up to three times. For instance, III is 3.
Rule 3: Subtraction Method
If a smaller number is placed before a larger number, we subtract the smaller number from the larger number. For example, XL → L - X → 50 - 10 = 40.
Rule 4: Limitation Rule
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. Similarly, 8 is written as VIII, not IIIIIIII.
Let’s now learn how to write 45 in Roman numerals. Follow these methods to write the number in Roman numerals:
In the expansion method, based on place value, the number is broken down. In this section, we will learn how to write 45 in Roman numerals using the expansion method.
To write 45 in Roman numerals, follow these steps:
Step 1: Break down the number based on place value—tens, ones, etc.
For 45, we write it as 40 + 5.
Step 2: Convert each number into Roman numerals:
40 in Roman numerals — XL
5 in Roman numerals — V
Step 3: Combine the Roman numerals together.
Therefore, 45 in Roman numerals is XL (40) + V (5) = XLV.
When writing a large number in Roman numerals, we group the number. To write 45 in Roman numerals, we group 45 as 40 + 5:
40 in Roman numerals — XL
5 in Roman numerals — V
So, 45 is written as XLV in Roman numerals.
Students often make mistakes when writing numbers in Roman numerals. To master Roman numerals, we can learn a few common mistakes and ways to avoid them.
A historian is studying ancient texts and discovers XLV artifacts in one location and XXV artifacts in another. Calculate the total number of artifacts.
The total number of artifacts is LXX.
The Roman numeral XLV is 45 and XXV is 25. The sum of 45 and 25 is 70, which is LXX in Roman numerals.
An architect is designing a building that will have CLXX floors, with XLV floors dedicated to residential use. How many floors are for non-residential use?
The number of non-residential floors is CXXV.
The total number of floors is CLXX (170), and XLV (45) floors are for residential use. Thus, 170 - 45 = 125 floors are for non-residential use. In Roman numerals, 125 is CXXV.
A museum has an exhibit that features XC sculptures. If XLV sculptures are on loan from another museum, how many sculptures belong to the museum permanently?
The number of sculptures that belong to the museum permanently is XLV.
The museum has XC (90) sculptures in total, with XLV (45) on loan. Therefore, 90 - 45 = 45 sculptures belong to the museum permanently, which is XLV in Roman numerals.
A craftsman is making XLV identical tables, and each requires III hours of work. Calculate the total number of hours needed to complete all the tables.
The total number of hours needed is CXXXV.
Each table requires III (3) hours, and there are XLV (45) tables. Thus, the total time is 45 × 3 = 135 hours. In Roman numerals, 135 is written as CXXXV.
A marathon runner completes a race in XLV minutes and then takes a break for XX minutes. Calculate the total time spent on the race and the break.
The total time spent is LXV.
The runner finishes the race in XLV (45) minutes and takes a XX (20) minute break. The total time is 45 + 20 = 65 minutes, which is LXV in Roman numerals.
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.