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Rerolling three dice to get the same multiset

Question

Roll three fair six-sided dice and note the values shown (ignoring which die shows which). Then roll all three again. What is the probability that the second roll shows exactly the same collection of values as the first?

Short answer

83/388883/3888. Condition on the first roll's pattern: all equal (prob 136\tfrac1{36}, then 11 matching ordered outcome), one pair (prob 512\tfrac5{12}, 33 matching outcomes) or all distinct (prob 59\tfrac59, 66 matching outcomes). Total: 1216(136+1512+309)=833888\tfrac{1}{216}\left(\tfrac1{36}+\tfrac{15}{12}+\tfrac{30}{9}\right)=\tfrac{83}{3888}.

Adapted from QuantQuestions.io; question and answer rewritten by SelfMadeQuant.com.

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