A) Average family size will be 2 children + 2 parents or a total of 4 people. B) Ratio of newborn boys to girls will be 1:1 For this, I will assume that each family will continue to have girl babies until a boy is born, then they will stop having children. So let's determine the number of girls that are born. 1/2 of all families will have a girl as their first child. 1/4 of all families will have a girl as their second child. 1/8 of all families will have a girl as their third child. The average number of girl children per family will be the limit of the infinite sequence 1/2 + 1/4 + 1/8 + 1/16 + ... + 1/(2^n) where n approaches infinity. The limit to the above equation is 1. So on average there will be 1 girl per family. Now each family continues to have children until they get a boy. So each family will have 1 boy. So the average family size will be 2 children. Half the families will only have 1 boy, 1/4th will have 1 girl, and 1 boy, 1/8 will have 2 girls and 1 boy, etc. So the average family size is only 2 children. And the ratio of boys to girls will be 1 to 1 as expected if the birth of a boy is just as likely as the birth of a girl.