"Imagine there is a country with a lot of people. These people do not die, the people consists of monogamous families only, and there is no limit to the maximum amount of children each family can have. With every birth there is a 50% chance its a boy and a 50% chance it is a girl. Every family wants to have one son: they get children until they give birth to a son, then they stop having children. This means that every family eventually has one father, one mother, one son and a variable number of daughters. What percent of the children in that country are male?"For the answer you can go back to my original post, last January, here (which also links back to the original Wiseman page):
--> Addendum: I just learned that there was a lengthy, interesting discussion of this puzzle over at MathOverflow a couple years back:
Be sure to read beyond where it says the question is "closed" to see all the commentary (in the end, under the usual assumptions, the answer remains 50/50).