Which of these is a valid Roman numeral? Support your answer with reason in each case.
CXXXXI

Answer

To determine whether "CXXXXI" is a valid Roman numeral, we will analyze it step by step.

### Step 1: Understand the components of the numeral
- The numeral "CXXXXI" consists of the following parts:
- C = 100
- XXXX = 4 X's
- I = 1

### Step 2: Analyze the repetition of 'X'
- In Roman numerals, the letter 'X' represents the value of 10.
- According to the rules of Roman numerals, a numeral can only repeat a letter up to three times in a row.

### Step 3: Check the repetition in "CXXXXI"
- In "CXXXXI", the letter 'X' appears four times in a row (XXXX).
- Since 'X' is repeated more than three times, this violates the Roman numeral rules.

### Step 4: Conclusion
- Therefore, "CXXXXI" is not a valid Roman numeral because it contains an invalid repetition of the letter 'X'.

### Final Answer
"CXXXXI" is not a valid Roman numeral because 'X' cannot be repeated more than three times in a row.

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