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MathNet 2017-part-07 — 172 problems (EN–VI) Question 148

Math Olympiad Vault · MathNet 2017-part-07 — 172 problems (EN–VI)

Question 148

There are 12 students in a classroom; 6 of them are Democrats and 6 of them are Republicans. Every hour the students are randomly separated into four groups of three for political debates. If a group contains students from both parties, the minority in the group will change his/her political alignment to that of the majority at the end of the debate. What is the expected amount of time needed for all 12 students to have the same political alignment, in hours?