Geometry

Question Analysis:  
This problem involves using contradiction to disprove the existence of a minimum value in the positive rational numbers.  
The key concept is assuming the opposite of the conclusion.

Key Concept Explanation:  
To prove a universal negative (e.g., "There is no such number"), we use contradiction:  
Assume there is such a number, and show this leads to a logical contradiction.

Step-by-Step Solution:  
1. Assume there is a smallest positive rational number, call it .  
2. Consider , which is also a positive rational number.  
3. But

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