rec.puzzles Archive

Suppose that it is equally likely for a pregnancy to deliver a baby boy as it is to deliver a baby girl.

probability/family

Problem

Suppose that it is equally likely for a pregnancy to deliver
a baby boy as it is to deliver a baby girl.  Suppose that for a
large society of people, every family continues to have children
until they have a boy, then they stop having children.
After 1,000 generations of families, what is the ratio of males
to females?
Show solution
The ratio will be 50-50 in both cases.  We are not killing off any
fetuses or babies, and half of all conceptions will be male, half
female.  When a family decides to stop does not affect this fact.