In this letter riddle, "Alone I am 24th, with a friend I am 20, another friend and I am unclean" – what am I?

Introduction / Context:
This is a classic riddle that blends knowledge of the English alphabet, Roman numerals and common slang. The statement says, "Alone I am 24th, with a friend I am 20, another friend and I am unclean." The answer is the letter X. When X stands alone, it is the 24th letter of the English alphabet. With another X, "XX" becomes the Roman numeral for 20. With a third X, "XXX" is commonly associated with adult, "unclean" content. This riddle is a good example of how a single symbol can have different meanings in different contexts.

Given Data / Assumptions:

• We are dealing with something that can be alone or combined with "friends".
• Alone, it is 24th, which suggests an alphabetical position.
• With one friend, it represents 20, which points towards Roman numerals.
• With another friend, it is associated with something unclean or adult rated.
• The answer is likely a single letter of the English alphabet.

Concept / Approach:
To decode the riddle, we first interpret "24th" as the position of a letter in the alphabet. The English alphabet has 26 letters, and the 24th letter is X. Next, we look at Roman numerals, where "XX" stands for 20. Finally, in modern media and rating systems, "XXX" is used to label explicit adult content, often called "unclean" in a moral sense. Only the letter X satisfies all three clues simultaneously, so it must be the answer.

Step-by-Step Solution:
Step 1: List the positions of letters in the alphabet and identify which one is 24th; this is the letter X. Step 2: Add one more X to form "XX" and interpret it as a Roman numeral, where X represents 10. Step 3: Compute 10 + 10 = 20, confirming that "XX" equals 20 in Roman numerals. Step 4: Add another X to form "XXX" and recall that this is a common mark for adult or explicit material. Step 5: Conclude that the symbol that fits all three clues is the letter X.

Verification / Alternative check:
As a check, test the other letter options. The letter C is the third letter, not the 24th, and does not form 20 when doubled. The letter L is 12th in the alphabet and equals 50 as a Roman numeral, so double L does not give 20. The Roman numeral V stands for 5, and "VV" is not a standard Roman numeral representation for 20. The number 4 is not even a letter and does not fit the radius of clues about alphabetical position. Therefore, no other choice explains all three statements together, while X does so perfectly, confirming its correctness.

Why Other Options Are Wrong:
The letter C: Alphabet position and Roman numeral value do not match the clues, and "CCC" is not associated with unclean content.
The number 4: Not a letter, so "alone I am 24th" does not apply, and other clues do not fit either.
The Roman numeral V: It has value 5, and "VV" is not 20, nor is "VVV" a standard symbol for adult material.
The letter L: It represents 50 in Roman numerals and is 12th in the alphabet, so it fails the 24th and 20 clues.

Common Pitfalls:
Many students may focus only on one of the clues, such as the alphabet position, and ignore the Roman numeral or slang aspects. Others might mistakenly assume that more than one letter could be 24th if they forget the exact order of the alphabet. A further pitfall is not recognising that "unclean" is a hint about adult content ratings. For multi clue riddles, it is essential to test each candidate against every clue, not just the first one that seems to fit, in order to reach a tightly justified answer.

Final Answer:
The object described as 24th alone, 20 with a friend, and unclean with two friends is the letter X.