Here's some background information : I was a campus tour guide at Brown University, which means that for one hour every week, I had to give a tour to prospective students and parents who are interested in the university. There were quite a few of us and we are all assigned individual time slots. On my slot, (Monday, 3PM) there were three other tour guides for a total of four. Now here's the scenario : there were three tour guides one day (one was sick) and about four prospective students. Clearly, only a single tour guide was necessary. But how do we choose which of us three has to give the tour in a fair and diplomatic way? Do we play rock-paper-scissors? But that could take ages. Here's the method : each of the tour guides picks a number from one to ten (inclusive). Then a prospective student does the same. Whoever is closest to the student's number has to give the tour. The others picked three and five, while I picked four. The number was five. I did not have ...