Rolls until consecutive values differ by two
Question
A fair six-sided die is rolled repeatedly. What is the expected number of rolls until two successive rolls differ by exactly ?
Short answer
. Group faces by how many follow-ups finish the game: faces have one partner and faces have two. Writing first-step equations for these two states, and , gives , , and the total is .
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Open the worked solutionLessons behind this question
- Expectation, Mean, and Variance
- Counting and Combinatorics
- Conditional Probability, Total Probability, and Bayes' Rule
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