Let the length of the Beginner's Trail be denoted as \( x \).
According to the problem:
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The Medium Trail is 1.2 times the length of the Beginner's Trail: \[ \text{Medium Trail} = 1.2x \]
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The Advanced Trail is 3.6 times the length of the Medium Trail: \[ \text{Advanced Trail} = 3.6 \times (1.2x) \]
Now let's calculate the length of the Advanced Trail:
\[ \text{Advanced Trail} = 3.6 \times 1.2x = 4.32x \]
This indicates that the Advanced Trail is 4.32 times as long as the Beginner's Trail.
Thus, the final answer is: \[ \boxed{4.32} \]