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Last updated on May 26th, 2025

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CDXXIX in Roman Numerals

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To meet their daily commerce and administration needs, the ancient Romans developed Roman Numerals. It used a combination of seven symbols — I, V, X, L, C, D, and M to represent numbers. Roman numerals were used to record transactions, keep track of data, and label military units. In this topic, we are going to learn about the Roman numeral CDXXIX.

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What is CDXXIX in Roman Numerals?

Ancient Romans discovered that counting fingers could get very complicated after 10. So to overcome the complexity, the Roman numeric system was developed. This was widely used throughout Europe as a standard writing system until the late Middle Ages.

 

Seven symbols are used to represent numbers in the Roman numeric system — I, V, X, L, C, D, and M. The numerals are made up of different combinations of these symbols. CDXXIX in Roman numerals can be written in number form by adding and subtracting the values of each Roman numeral, i.e., CDXXIX = 429.

 

Let us learn more about the Roman numeral CDXXIX, how we write it, the mistakes we usually make, and ways to avoid these mistakes.

 

cdxxix roman numerals

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Basic Rules for CDXXIX in Roman Numerals

When writing Roman numerals, there are a few rules that we need to follow based on the Roman numerals we are trying to write. In this section, we will learn about the rules when writing Roman numerals and how to represent them.

 

Rule 1: Addition Method:

When a larger symbol is followed by a smaller symbol, we add the numerals to each other. For example, VIII = 5 + 3 = 8.

 

Rule 2: Repetition Method:

A symbol that is repeated three times in continuation increases the value of the numeral. For example, XXX = 30.

 

Rule 3: Subtraction Method:

We use the subtraction method when a smaller symbol precedes a larger symbol. For example, XL = 40 (which is 50 – 10).

 

Rule 4: Limitation Rule:

Symbols cannot be repeated more than three times, and some symbols, such as V, L, and D, cannot be repeated more than once. For example, 10 is represented as X and not VV.

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How to Write CDXXIX in Roman Numerals?

Let us learn about how to write CDXXIX in Roman numerals. There are two methods that we can use to write Roman numerals:

 

  • By Expansion Method
  • By Grouping Method
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CDXXIX in Roman Numeral by Expansion Method

The breaking down of Roman numerals into parts and then converting them into numerals is what we call the expansion method. The expansion method involves breaking down Roman numerals into numerical form and adding or subtracting them to get the final number.

 

Step 1: Break the Roman numerals into parts.

 

Step 2: Now write each of the Roman numerals with its numerical digit in the place value.

 

Step 3: Add or subtract the numerals together.

 

For CDXXIX,

 

Step 1: First we break the Roman numerals. CDXXIX = C + D + X + X + I + X

 

Step 2: Write the Roman Numerals for each part. The Roman Numeral C is 100 The Roman Numeral D is 500 The Roman Numeral X is 10 The Roman Numeral I is 1

 

Step 3: Combine all the numbers considering the subtraction rule. CDXXIX = 400 + 20 + 9 = 429.

 

Therefore, the Roman Numeral CDXXIX is 429.

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CDXXIX in Roman Numeral by Grouping Method

Using subtraction and addition rules, we will apply the grouping method. This means we break the Roman numerals into smaller groups, which makes it easier to work with. This method groups the Roman numerals logically, and then we write the numbers for each group.

 

Step 1: Take the largest number and write the number for that Roman numeral.

 

Step 2: Write the Roman numeral using the subtraction and addition rules.

 

Example: Let’s take the Roman numeral CDXXIX.

 

Step 1: The larger Roman numerals are what we will begin with. Once split, the Roman numerals we get are CD, XX, and IX. The numeral for CD is 400. The numeral for XX is 20.

 

Step 2: Now we need to either add or subtract the smaller number, depending on its place.

Here we add XX and IX to CD and we will get CDXXIX. The Roman numeral IX is 9. Therefore, the numeral of CDXXIX is 429.

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Common Mistakes and How to Avoid Them in CDXXIX Roman Numerals

Students can make mistakes when studying Roman numerals. Here are a few common mistakes students make, and ways to avoid them.

Mistake 1

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Mistakes when applying the repetition method

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It can be quite confusing for beginners to remember that Roman Numerals cannot be repeated more than three times. Another thing to keep in mind is that Roman Numerals such as V, L, and D cannot be repeated.

 

For example, writing LL as 100 is incorrect; the correct answer is C.

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CDXXIX Roman Numerals Examples

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Problem 1

Calculate the sum of CDXXIX + LXXI. Write the answer in Roman numerals.

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The sum is D

Explanation

Convert both Roman numerals into their decimal form:

CDXXIX = 429

LXXI = 71

Now add both numbers: 429 + 71 = 500

Now convert the number into its Roman numeral. 500 = D

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Problem 2

What is the difference between CDXXIX - CXXIX? Write in Roman numerals.

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The difference is CCC

Explanation

Convert the Roman numerals into their decimal form:

CDXXIX = 429

CXXIX = 129

Now we subtract the numbers, 429 - 129 = 300

Convert the number into its Roman numeral, 300 = CCC

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Problem 3

Divide CDXXIX by 3 and write the answer in Roman numerals.

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CXLIII

Explanation

Convert CDXXIX into its decimal form:

CDXXIX = 429

Divide by 3: 429 / 3 = 143

Write 143 in Roman numerals: 100 (C) + 40 (XL) + 3 (III) = CXLIII

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Problem 4

Find the product of CDXXIX and II.

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DCCCLVIII is the product of CDXXIX and II.

Explanation

Write CDXXIX and II in numbers:

CDXXIX = 429

II = 2

Multiply the numbers, 429 × 2 = 858

Convert 858 into its Roman numerals, 800 (DCCC) + 50 (L) + 8 (VIII) = DCCCLVIII

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Problem 5

Convert CDXXIX into its decimal form.

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In decimal form, CDXXIX is 429

Explanation

Break CDXXIX into components, CD = 400 (500 - 100) XX = 20 (X + X) IX = 9 (X - I) Add values: 400 + 20 + 9 = 429

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FAQs on CDXXIX in Roman Numerals

1.What is IX in Roman numerals?

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2.Is CDXXIX a prime number?

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3.What is CDXXIX + CDXXIX?

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4.What is CDXLIX?

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5.Subtract XX from CDXXIX

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Important Glossaries for CDXXIX in Roman Numerals

  • Limitation Rule: There are some symbols that cannot be repeated more than once (V, L, D). For example, writing VV for 10 is wrong; the correct answer is X.

 

  • Subtraction Rule: This rule states that when a smaller numeral precedes a larger one, you subtract the smaller from the larger. Example: IX = 9.

 

  • Grouping Method: A method of breaking a Roman numeral into smaller groups to simplify calculation.

 

  • Place Value: The position of a digit in a number, which determines its value. For example, the number 4 in 429 is in the hundreds place.

 

  • Composite Number: A number that has more than two factors. For example, 429 is a composite number with factors including 1, 3, 11, 13, 33, 39, 143, and 429.
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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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