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Last updated on May 26th, 2025

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400 in Roman Numerals

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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 used in royal titles, book names, sequences, and more. Here we will be discussing Roman Numerals, rules, and examples.

400 in Roman Numerals for Filipino Students
Professor Greenline from BrightChamps

What is 400 in Roman Numerals?

The royal titles, such as Henry I, Henry II, and so on, use Roman Numerals. Have you noticed these names and wondered what the symbols (I and II) represented? Those are Roman Numerals. In earlier times, people used fingers, sticks, and bones to count. As life became complex, a standard form was required, and the ancient Romans developed the Roman Numeral system. The symbols I (1), V (5), X (10), L (50), C (100), D (500), and M (1000) are used.

 

In Roman Numerals, we use CD to represent 400. Here, C is 100, and D is 500. Let’s learn more about Roman numerals and how we write them.

400 in roman numerals

Professor Greenline from BrightChamps

Basic Rules for 400 in Roman Numerals

There are certain basic rules for writing numbers in Roman Numerals. Let's discuss these rules that need to be remembered when writing numbers.

 

Rule 1: Addition Method

The addition method is used when a smaller number is placed after a larger number. For example, VI → V + I → 5 + 1 = 6.

 

Rule 2: Repetition Method

Certain Roman Numerals can be repeated up to three times. For example, CCC → 300.

 

Rule 3: Subtraction Method

If a smaller number precedes a larger number, we subtract the smaller number from the larger number. For example, XC → C - X → 100 - 10 = 90.

 

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 use XL for 40 instead of XXXX.

Professor Greenline from BrightChamps

How to Write 400 in Roman Numerals

Let’s now learn how to write 400 in Roman Numerals. Follow these methods to write the number in Roman Numerals.

 

  • By Expansion Method  

 

  • By Grouping Method
Professor Greenline from BrightChamps

400 in Roman Numeral by Expansion Method

In the expansion method, based on place value, the number is broken down. In this section, we will learn how to write 400 in Roman numerals using the expansion method.

 

To write 400 in Roman Numerals, follow these steps:

 

Step 1: Break the number based on place value. Place values are ones, tens, hundreds, etc.

 

For 400, we write it as 500 - 100

 
Step 2: Convert the numbers into Roman Numerals  


500 in Roman Numeral — D  


100 in Roman Numeral — C

 
Step 3: Apply the subtraction method.  


Therefore, 400 in Roman Numeral is D (500) - C (100) = CD  

Professor Greenline from BrightChamps

400 in Roman Numeral by Grouping Method

When writing a large number in Roman Numerals, group the numbers.  


To write 400 in Roman Numerals, we group 400 as 500 - 100.  


500 in Roman Numeral — D  


100 in Roman Numeral — C  


So, 400 is written as CD in Roman Numerals.  

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Common Mistakes and How to Avoid Them in 400 Roman Numerals

Students often make mistakes when writing numbers in Roman Numerals. Here are some common mistakes and ways to avoid them.

Mistake 1

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Errors in the repetition method

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The repetition method can be confusing as Roman Numerals cannot be repeated more than three times. Symbols like V, L, and D cannot be repeated.
 

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400 in Roman Numerals Examples

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Problem 1

A historian finds two ancient artifacts labeled CC and CC. What is the total historical value of both artifacts in Roman numerals?

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The total historical value of both artifacts is CD.
 

Explanation

The value of each artifact is given as CC, which is 200. Adding them together:  
CC + CC = 200 + 200 = 400.

 
400 in Roman numerals is written as CD.
 

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Problem 2

A museum wants to display CD relics equally across L display cases. How many relics will each display case contain?

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Each display case will contain VIII relics.

Explanation

To find the number of relics per display case, divide the total number of relics by the number of display cases:  


CD / L  


CD = 400  


L = 50  


Therefore, 400 / 50 = 8.  


8 in Roman numerals is written as VIII.

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Problem 3

A collector has CLXX and needs CCC more to reach CD. How many more does he need in Roman numerals?

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He needs CCXXX more.
 

Explanation

The collector has CLXX, which is 170, and he needs to reach CD, which is 400.  
400 - 170 = 230.  


230 in Roman numerals is CCXXX.
 

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Problem 4

Calculate the difference between CD and CCL.

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The difference between CD and CCL is CL.

Explanation

CD = 400  


CCL = 250

 
The difference is 400 - 250 = 150.

 
150 in Roman numerals is written as CL.

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Problem 5

Write the Roman numeral for 200 + 200 using the expansion method.

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The Roman numeral for 200 + 200 is CD.
 

Explanation

Step 1: Convert the numbers 200 and 200 into Roman numerals:  


200 - CC  


200 - CC  

 

Add the numbers together: 200 + 200 = 400  


Using the expansion method: 400 = 100 + 100 + 100 + 100 = CD.

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FAQs on 400 in Roman Numerals

1.What is 90 in Roman numerals?

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2.How to write 400 in Roman numerals?

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3.What is 450 in Roman Numerals?

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4.Is CD a prime number?

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5.What are the multiples of 400?

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6.How can children in Philippines use numbers in everyday life to understand 400 in Roman Numerals?

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7.What are some fun ways kids in Philippines can practice 400 in Roman Numerals with numbers?

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8.What role do numbers and 400 in Roman Numerals play in helping children in Philippines develop problem-solving skills?

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9.How can families in Philippines create number-rich environments to improve 400 in Roman Numerals skills?

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Professor Greenline from BrightChamps

Important Glossaries for 400 in Roman Numerals

  • Addition rule: Used when a large number is followed by a smaller numeral, and the values are added. For example, VI = V + I = 5 + 1 = 6.

 

  • Subtraction rule: Used when a smaller numeral precedes a larger one, and the smaller is subtracted from the larger. For example, CD = D - C = 500 - 100 = 400.

 

  • Grouping method: Group numbers based on their place value and convert each group into Roman numerals. For example, 400 = 500 - 100 = CD.

 

  • Repetition rule: Certain symbols (I, X, C, M) can be repeated up to three times. For example, CCC = 300.

 

  • Limitation rule: Symbols like V, L, and D cannot be repeated. For instance, XL is used for 40 instead of XXXX.
Professor Greenline from BrightChamps

About BrightChamps in Philippines

At BrightChamps, numbers are more than just digits—they are keys to limitless possibilities! Our goal is to help children throughout the Philippines develop crucial math skills, focusing today on the 400 in Roman Numerals with a special focus on Roman numerals—in a lively, fun, and easy-to-follow way. Whether your child is calculating the speed of a roller coaster at Enchanted Kingdom, keeping track of scores at a basketball game, or managing their allowance to buy the newest gadgets, mastering numbers builds confidence for daily life. Our interactive lessons make learning fun and easy. Since kids in the Philippines learn in diverse ways, we tailor our approach to fit each child’s unique style. From the bustling streets of Manila to the beautiful islands of Palawan, BrightChamps brings math to life, making it relatable and exciting throughout the Philippines. Let’s make Roman numerals a fun part of every child’s learning journey!
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Hiralee Lalitkumar Makwana

About the Author

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.

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Fun Fact

: She loves to read number jokes and games.

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