421 in Roman Numerals

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 to count using fingers, sticks, bones, etc. 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 CDXXI to represent 421, here CD is 400, 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, VI → V + I → 5 + 1 = 6.

Rule 2: Repetition Method

Certain Roman numerals can be repeated up to three times. For example, III → 3.

Rule 3: Subtraction Method

If a small number precedes 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 don't write VV for 10; instead, we use X.

Let’s now learn how to write 421 in Roman numerals. Follow these methods to write the number in Roman numerals.

• By Expansion Method
• By Grouping Method

In the expansion method, based on the place value, the number is broken down. In this section, we will learn how to write 421 in Roman numerals using the expansion method. To write 421 in Roman numerals, follow the steps:

Step 1: Break the number based on place value: hundreds, tens, ones. For 421, we write it as 400 + 20 + 1.

Step 2: Convert the numbers into Roman numerals.

400 in Roman numerals — CD

20 in Roman numerals — XX

1 in Roman numerals — I

Step 3: Combine the Roman numerals together. Therefore, 421 in Roman numerals is CD + XX + I = CDXXI.

When writing a large number in Roman numerals, we group the number. To write 421 in Roman numerals, we group 421 as 400 + 20 + 1.

• 400 in Roman numerals — CD
   
• 20 in Roman numerals — XX
   
• 1 in Roman numerals — I

So, 421 is written as CDXXI in Roman numerals.

Roman numerals follow a certain pattern, making them look similar. In this section, we will learn some numbers related to the Roman numeral 421.

• Addition rule: The addition method is used when a smaller numeral follows a larger numeral, and their values are added. For example, XI = X + I = 10 + 1 = 11.

• Subtraction rule: The subtraction method is used when a smaller numeral precedes a larger numeral, subtracting the smaller value. For example, CD = D - C = 500 - 100 = 400.

• Repetition rule: Certain symbols (I, X, C, M) in the Roman numeric system can be repeated only up to three times. For example, III = 3 (I is repeated three times to represent the number 3).

• Expansion method: A method where numbers are broken down based on place value and converted into Roman numerals.

• Grouping method: Here the given numbers are grouped based on their place value and then converted into their Roman numerals. For example, 421 = 400 + 20 + 1 = CDXXI.