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I've an unfair coin which has the probability of the head =70%, I toss the coin the first time and I get a tail. Now how many time do I need to flip the coin so that the number of heads is equal to the number of tails.
My solution: As I already have one tail, I need n-1 tail and n heads. If I have 3 coin tosses, I expect 2.1 expectations of heads and 0.9 of tails expectation. So I answered 3. I'm not sure if this is the right way to solve, feel free to clarify anything that seems unclear