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MathNet 2018-part-07 — 177 problems (EN–VI) Question 19

Math Olympiad Vault · MathNet 2018-part-07 — 177 problems (EN–VI)

Question 19

Rachel has the number $1000$ in her hands. When she puts the number $x$ in her left pocket, the number changes to $x+1$. When she puts the number $x$ in her right pocket, the number changes to $x^{-1}$. Each minute, she flips a fair coin. If it lands heads, she puts the number into her left pocket, and if it lands tails, she puts it into her right pocket. She then takes the new number out of her pocket. If the expected value of the number in Rachel's hands after eight minutes is $E$, then compute $\left\lfloor\frac{E}{10}\right\rfloor$.