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Rational lions and a piece of meat

Question

A cage holds nn perfectly rational lions and one piece of meat. A lion that eats meat falls asleep and thereby becomes meat that another lion can eat. Every lion would like to eat, but above all wants not to be eaten. What happens, depending on nn?

Short answer

The meat is eaten if nn is odd and left alone if nn is even. One lion eats freely. With two, the eater would be eaten, so neither moves. With nn lions, eating leaves n−1n-1 lions and fresh meat, which is safe exactly when n−1n-1 is even; induction gives the parity rule.

Adapted from Joshi, Denson & Downes, Quant Job Interview Questions and Answers, Q8.17, p.277; question and answer rewritten by SelfMadeQuant.com.

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