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Last updated on May 26th, 2025

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128 in Roman Numerals

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Roman numerals are a way of expressing numbers using symbols. I, V, X, L, C, D, and M are the symbols used. Roman numerals are used in royal titles, book names, sequences, and so on. Here we will be discussing Roman numerals, rules, and examples.

128 in Roman Numerals for US Students
Professor Greenline from BrightChamps

What is 128 in Roman Numerals?

Royal titles, such as Henry I, Henry II, and so on, often use Roman numerals. These symbols (I and II) represent numbers. Earlier, people used to count using fingers, sticks, bones, etc. As life became more 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 used for counting.

 

In Roman Numerals, we use CXXVIII to represent 128, where C is 100, XX is 20, and VIII is 8. Let’s learn more about Roman numerals and how we write them.

128 in roman numerals

Professor Greenline from BrightChamps

Basic Rules for 128 in Roman Numerals

There are certain basic rules for writing 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, VIII → V + I + I + I → 5 + 1 + 1 + 1 = 8.

 

Rule 2: Repetition Method

To write a large number, certain Roman numerals can be repeated up to three times. For instance, XXX → 30.

 

Rule 3: Subtraction Method

If a smaller number precedes a larger number in Roman numerals, we subtract the smaller number from the larger 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, and 8 is written as VIII, not IIIIIIII.

Professor Greenline from BrightChamps

How to Write 128 in Roman Numerals

Let’s now learn how to write 125 in Roman numerals. Follow these methods to write the number in Roman numerals.

  • By Expansion Method

 

  • By Grouping Method
Professor Greenline from BrightChamps

128 in Roman Numerals by Expansion Method

In the expansion method, based on the place value, the number is broken down. In this section, we will learn how to write 128 in Roman numerals using the expansion method.

 

To write 128 in Roman numerals, follow these steps:

 

Step 1: Break the number based on the place value into hundreds, tens, and ones.

 

For 128, we write it as 100 + 20 + 8.

 

Step 2: Convert each component into Roman numerals.


 100 in Roman numerals is C.
 20 in Roman numerals is XX.
 8 in Roman numerals is VIII.

 

Step 3: Combine the Roman numerals together.


Therefore, 128 in Roman numerals is C (100) + XX (20) + VIII (8) = CXXVIII.

Professor Greenline from BrightChamps

128 in Roman Numerals by Grouping Method

When writing a large number in Roman numerals, we group the numbers. To write 128 in Roman numerals, group 128 as 100 + 20 + 8.


100 in Roman numerals is C.
20 in Roman numerals is XX.
8 in Roman numerals is VIII.

 

So, 128 is written as CXXVIII in Roman numerals.

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Common Mistakes and How to Avoid Them in 128 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.

Mistake 1

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Errors in Repetition Method
 

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The repetition method can be confusing for beginners as it states that Roman numerals cannot be repeated more than three times. In addition, some Roman numerals such as V, L, and D cannot be repeated.

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128 in Roman Numerals Examples

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Problem 1

A historian is analyzing ancient manuscripts and finds that the value of a scroll is written as CXXVIII. The historian finds another scroll valued at LXXX. What is the total value of both scrolls in Roman numerals?

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The total value of both scrolls is CCVIII.

Explanation

The values of the scrolls are CXXVIII = 128 and LXXX = 80. Adding them gives 128 + 80 = 208. The Roman numeral for 208 is CCVIII.
 

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Problem 2

A merchant has a stockpile of CXLVIII gemstones. After selling XX gemstones, how many gemstones does the merchant have left?

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The merchant has CXXVIII gemstones left.
 

Explanation

The merchant originally has CXLVIII = 148 gemstones. After selling XX = 20 gemstones, the remaining gemstones are 148  20 = 128. In Roman numerals, 128 is written as CXXVIII.
 

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Problem 3

Calculate the difference between CXXVIII and LXXII.

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The difference between CXXVIII and LXXII is LVI.
 

Explanation

The numbers are CXXVIII = 128 and LXXII = 72. Subtracting them gives 128  72 = 56. The Roman numeral for 56 is LVI.

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Max, the Girl Character from BrightChamps

Problem 4

A museum is cataloging artifacts and finds that the combined weight of two artifacts is CXXVIII kilograms. If one artifact weighs XLV kilograms, what is the weight of the second artifact?

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The weight of the second artifact is LXXXIII kilograms.
 

Explanation

The total weight is CXXVIII = 128 kilograms, and one artifact weighs XLV = 45 kilograms. The weight of the other artifact is 128  45 = 83. The Roman numeral for 83 is LXXXIII.
 

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Problem 5

Convert the sum of 100 and 28 into Roman numerals using the expansion method.

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The Roman numeral for 100 + 28 is CXXVIII.
 

Explanation

Step 1: Convert the numbers 100 and 28 into Roman numerals.


100 = C


28 = XXVIII

 

Add the numbers: 100 + 28 = 128.


Using the expansion method: 128 = 100 + 20 + 8 = CXXVIII.

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FAQs on 128 in Roman Numerals

1.What is 9 in Roman Numerals?

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2.How to Write 128 in Roman Numerals?

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3.What is 135 in Roman Numerals?

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4.Is CXXVIII a Prime Number?

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5.What are the Multiples of 128?

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6.How can children in United States use numbers in everyday life to understand 128 in Roman Numerals?

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7.What are some fun ways kids in United States can practice 128 in Roman Numerals with numbers?

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8.What role do numbers and 128 in Roman Numerals play in helping children in United States develop problem-solving skills?

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9.How can families in United States create number-rich environments to improve 128 in Roman Numerals skills?

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Professor Greenline from BrightChamps

Important Glossary for 128 in Roman Numerals

  • Addition Rule: The addition method is used when a larger number is followed by a smaller numeral, and the values are added. For example, CXXVIII = C + XX + VIII = 100 + 20 + 8 = 128.

 

  • Grouping Method: Here, the given number is grouped based on place value, and we convert each group into its Roman numeral. For example, 128 = 100 + 20 + 8 = CXXVIII.

 

  • Repetition Rule: Certain symbols (I, X, C, M) in the Roman numeral system can be repeated only up to three times. For example, XXX = 30 (X is repeated three times to represent 30).

 

  • Subtraction Method: A smaller numeral before a larger one indicates subtraction. For example, IV = 5  1 = 4.

 

  • Limitation Rule: Roman numeral symbols cannot be repeated more than three times, and some symbols like V, L, and D cannot be repeated at all.
Professor Greenline from BrightChamps

About BrightChamps in United States

At BrightChamps, we understand numbers are more than symbols—they unlock endless possibilities! Our goal is to guide children across the United States in mastering essential math skills, focusing today on the 128 in Roman Numerals with special attention to Roman numerals—in a fun, engaging, and easy-to-understand way. Whether your child is calculating how quickly a roller coaster zips through Disney World, tracking scores at Little League baseball games, or budgeting their allowance for cool gadgets, having solid number skills builds their confidence for daily tasks. Our interactive lessons make learning enjoyable and straightforward. Since kids across the USA have unique learning styles, we customize our methods to match each child. From the vibrant streets of New York City to the sunny beaches of California, BrightChamps makes math come alive, relatable, and exciting throughout America. Let’s bring Roman numerals to life on every child’s math path!
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