Problem of the Week

Problem of the Week

The Problem: In a certain tribe, all families want girls. They keep having babies until a girl is born. What is the expected ratio of boys and girls in this tribe assuming girls and boys are equally likely to be born?

Hint: Focus separately on 1st born, 2nd born,etc.

Solution: 1st born, 2nd born, 3rd born, and so on, are all equally likely to be boys or girls so the expected ratio of boys to girls is .

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