XL in Roman Numeral

The number 40 in Roman numerals is written as XL. X stands for 10 and L stands for 50. When you put an X before L you take away 10 from 50 which equals 40. So, XL is the number 40 in Roman Numerals.

40＝ⅩⅬ

Rule 1: Addition Rule

Addition rule: In this rule, we sum two values to get the required number. When the smaller number succeeds the larger number, then these numbers are added together.

For example, X (10) plus XX (20) makes XXX (30).

Ⅹ + ⅩⅩ = ⅩⅩⅩ    or    10 + 20 = 30

Rule 2: Repetition Rule

In this rule, the numbers repeat themselves to get the desired number, but the numbers cannot be repeated more than thrice. For example, II is 2, and III is 3, but you can't do the same for 6.

 II is 2 
Ⅲ is 3 
ⅡⅢⅠ is not 6 

Rule 3: Subtraction Rule,

In this rule, the difference of two numbers gives the desired value. The greater number is written after the smaller number, the smaller number is subtracted from the greater one.

 XL means 50 (L) minus 10 (X), which equals 40.

Ⅼ - Ⅹ = ⅩⅬ    or    50 - 10 = 40

Rule 4: Limitation Rule
Roman numerals cannot be repeated more than thrice. This limitation cannot be used for number 4(IIII) and so on.  For example, you can't write XXXX for 40; we write XL instead.

ⅩⅩ  correct 
ⅩⅩⅩⅩ  wrong
ⅩⅬ  correct
 

In roman numerals, we write 40 as XL, to get the desired number, we use subtraction and addition rule and combine them. We write roman numerals in methods explained below:

• Expansion method

• Grouping method
   

This method includes parting down numbers based on their place values like thousands, a hundred, tens, and ones respectively. Every place value is written in the form of roman numerals. The steps for this method are as shown below:

• Expand and part down the numbers into place values.

• Change the place values of numbers into roman numerals.

• Join the roman numerals to get the desired value.

So, when you combine them, 40 in the Roman Numeral is written as XL.
 

This method involves breakdown of large numerals into small parts based on their Roman numeral values. This method works as follows:

• Identify symbols: Look for roman numerals that should be added or subtracted together according to addition and subtraction rules, as discussed.

• Breaking down larger numbers into smaller ones.

• Add or subtract values of the smaller numerals.

• So, you can group three 10s as XXX and add a V to write 35 as XXXV.

Example:

1. CXLIX

C→100

XL→50-10=40

IX→9

Add: 100+40+9=149.

So, while you can group four Xs as XXXX, the best way to write 40 is XL!

Example: 

1. CXL:

C=100

XL=40

Adding, 100+40=140,CXL.

Take a look at some numbers that are related to 40 in Roman Numerals

XXXIX - 39 (subtracting I from XL, which is 40)

XXXVIII - 38 (subtracting II from XL)

XXXVII - 37 (subtracting III from XL)

XLII - 42 (adding II to XL)

XLIII - 43 (adding III to XL)

XLIV - 44 (adding IV to XL)

XLV - 45 (adding V to XL)
 

• Grouping Method: Combining smaller numerals to express a larger number (e.g., thinking of 11 as an X and I that’s XI).

• Limitation Rule: The rule stating that numerals like I, X, and C can only be repeated up to three times.