Here are some examples of how you can tempt your friends to accept attractive-looking bets. But mathematical analysis shows that these bets are unfair. Mathematical tricks and curiosities are presented like: the magic number 70 in exponential growth; how to estimate the birth-and mortality rate in your town; why the best team does not always win; the famous TV-Show of Monty Hall with the car and the two goats behind three doors; the story behind the fairy tales of the 1\'001 Arabian nights; why the last judgment occurs in 800 years; etc. Finally there is a long list of easy and difficult riddles.