Probability theory and modeling (Q1897200)

This paper describes some elementary problems, which are a little bit more hard than the usual ones, but which nevertheless can be dealt with in the last year of Switzerland highschool. Three examples are given. The waiting time problem is illustrated with two examples which at first glance do not exhibit common features, then martingales are simply introduced in the ruin problem, and lastly one considers propagation of rumor in population.