Last queen before last king given an early pattern
Question
A standard -card deck is shuffled. Eve will win $100 if the final queen in the deck comes before the final king. Her friend looks through the deck and tells her that exactly two queens come before the first king. With this information, what are Eve's expected winnings?
Short answer
$60. Only the relative order of the kings and queens matters, and all orders are equally likely. The hint fixes the first three as queen, queen, king, leaving queens and kings in random order; Eve wins iff the last of these is a king, probability .
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Open the worked solutionLessons behind this question
- Counting and Combinatorics
- Expectation, Mean, and Variance
- Conditional Expectation and Variance Revisited
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