Simple Random Walk with equal probability of +1 and -1.

Question

You have 1D random Walk, with +1 of probability 0.5, and -1 of probability 0.5.

What is the probability that you will reach +10 but never exceed -5?

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Attempt: The probability of getting +10 is easy, it is just 0.5^10. But I don't know how to factor in the -5 part.

Answer 1

Hint:

Take a look at Gambler's ruin.