To my students:

Consider the following scenario:

In the country of Amazonia boys are valued but girls are worshipped. No mother, however, wants to give birth to multiple girls in order to avoid succession struggles related to the leadership of the family. Thus, every mother gives birth to children precisely until a daughter is born to her.

a) If the probability of giving birth to a son is .5, what ratio of newborns in Amazonia are girls?

b) If the probability of giving birth to a son is 0<s<1, what ratio of newborns in Amazonia are girls?