Last week's first issue attracted the attention of our regular commenters and led to interesting observations (see comments from Author's riddles). The key is to realize that since the narrator questions the other nine people present and finds out that they have all shaken a different number of hands, and since no one shakes their partner's hand, the number of shakes each person shakes. people consulted will be, respectively, 0, 1, 2, 3, 4, 5, 6, 7 and 8. Therefore, the partner of the person who has shaken 8 hands has not shaken any (he is the only candidate for 0 shakes, since all the other people have shaken their partner's hand). Similarly, the person who has shaken 7 hands is paired with the person who has shaken 1 (that is, with whom he has only shaken the hand of the person who has shaken 8), the one who has shaken 6 with the one who has shaken 2, the one who has shaken 5 with whom he has shaken 3, and the one who has shaken 4 is the narrator's partner, who has also shaken 4. It is easier to see by making a diagram in which each of the 10 people is represented with a dot and each shake of hands with a line joining two points.
