The Coin Problem

An interesting problem is the following: In a land with only denominations of $6 and $11, what is the largest integral expense that cannot be paid. Examples of expenses that cannot be paid in this strange land are 1, 2, 3, 4, 5, 7, 8, 9, 10. However, how do we find the largest such instance? It…

A Puzzle About Births

I came across this nice puzzle: In a faraway land long ago, boys were valued more than girls. So couples kept having babies until they had a boy. What is the ratio of girls to boys in this strange land? Assume that the birth of a boy and a girl is equally likely. Trying to solve…