Expected Rolls to Reach Position 10 in a Symmetric Random Walk
You start at position $0$ on the number line. Each turn, you roll a fair six-sided die and get a result $X$.
- If $X \in \{1, 2, 3\}$, you move $X$ steps to the right.
- If $X \in \{4, 5, 6\}$, you move $X - 3$ steps to the left (i.e., 1, 2, or 3 steps left).
The process ends when you first reach position
0$ or higher. How many rolls does it take on average?
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