có 5 bạn nữ và 4 bạn nam có bao nhiêu cách sắp xếp sao cho bạn nữ ngồi xen kẻ bạn nam

To solve this problem, we can use the concept of permutations. We have 5 female friends and 4 male friends. We want to arrange them such that a female friend sits next to a male friend. First, we can choose one of the 5 female friends in 5 ways. Then, for each choice of a female friend, there are 4 ways to choose a male friend to sit next to her. After choosing the pair of friends, we have 4! ways to arrange the remaining 4 female friends and 3 male friends among themselves. So, the total number of arrangements is: \[5 \times 4 \times 4! \times 3! = 5760\] Therefore, there are 5760 ways to arrange the friends as required.