Five married couples will sit around a round table. Although every sitting spot is marked by a name card, they do not notice the cards and sit randomly. Then, they realize that none of them is sitting on the spot marked for them or their spouses.
In how many different ways can this situation occur?
1. A person is not required to sit next to her/his spouse.
2. The number of different ways should be calculated given a fixed placement of name cards.
answers: # 55
popularity: 64.3 %
difficulty: 64.3 %