Guessing a deck of three aces and three jacks
Question
A face-down pile contains exactly aces and jacks in random order, and Jamie knows this. Cards are turned over one at a time; before each card is revealed Jamie guesses whether it is an ace or a jack, winning for each correct guess. Playing all cards optimally, how much does Jamie expect to win?
Short answer
. Always guess the type with more cards remaining (either on a tie). By backward induction, or by summing the turn-by-turn success probabilities , the expected total is .
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Open the worked solutionLessons behind this question
- Optimisation Problems
- Constrained Optimisation and Lagrange Multipliers
- Sample Spaces, Events, and the Probability Axioms
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