Insight · ★★★☆☆ · ~5 min
The Gender Ratio Trap, Part 2
Same country, same rule — a new question with a surprising answer.
by MindYourPuzzle
You solved the first Gender Ratio Trap: every family keeps having children until they have a girl, then stops. The population ratio of boys to girls is exactly 1:1 — a stopping rule cannot change the 50/50 odds of any birth.
Now the sequel.
Same country, same rule. Instead of counting all children, you knock on ONE random family's door and ask: what fraction of YOUR children are girls?
Averaged over all families, what is the expected fraction of girls in a family?
%
Hints