Mathematical Methods in the Physical Sciences · Problem 16.2.13
FUNCTIONS OF A COMPLEX VARIABLE — Mary Boas
Mathematics — Methods · probability-sample-space
Problem
A student claims in Problem 1.5 that if one child is a girl, the probability that both are girls is 21. Use appropriate sample spaces to show what is wrong with the following argument: It doesn't matter whether the girl is the older child or the younger; in either case the probability is 21 that the other child is a girl.