Position of the first ace

Cards are drawn one by one from a well-shuffled 52-card deck. What is the expected position of the first ace?

Show hints (2)+
  1. Think of the 4 aces creating 5 gaps among the 48 other cards.
  2. By symmetry each gap has the same expected size.

Answer

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10.6 (± 0.1)

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Asked at: Jane Street, SIG

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