Cards between the first two and the first ace
Question
A standard -card deck is shuffled and dealt face up one card at a time. Suppose the first comes out before the first ace. Under this condition, what is the expected number of cards dealt strictly between the first and the first ace?
Short answer
(about 8.42). The 8 aces and 2s split the other 44 cards into 9 gaps of average size . Given a 2 leads, the remaining three 2s fall before the first ace on average times, so gaps are spanned. The answer is .
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Open the worked solutionLessons behind this question
- Expectation, Mean, and Variance
- Conditional Probability, Total Probability, and Bayes' Rule
- Worked Examples — Probability Trees, Monty Hall, and Bayesian Updating
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