Safe spot in a circle of 2000 with every second removed
Question
Two thousand people stand in a circle numbered to . Person eliminates person and passes the sword to person , who eliminates person and passes it on, and so on around the circle, each holder removing the next living person and handing the sword to the following survivor. Which numbered position is the last one remaining?
Short answer
Position . This is the Josephus problem with step 2: writing with , the survivor is . Here , so the survivor is .
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Open the worked solutionLessons behind this question
- Sample Spaces, Events, and the Probability Axioms
- Conditional Probability, Total Probability, and Bayes' Rule
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