FEB VB 2010-01-01 !# Immigration - 落地生根
p*3
1 楼
6 members of a book club will exchange books.
each member will give his book to another member and get a book from a
different member.
no swapping occurs (2 member get each other's book).
how many ways to arrange the exchange?
(show thoughts, not just a number)
each member will give his book to another member and get a book from a
different member.
no swapping occurs (2 member get each other's book).
how many ways to arrange the exchange?
(show thoughts, not just a number)