Theorem 4.11: Let multiset S={n°a1,n2a2y…,nk·at},and n=n+n2+.+nk s. Then the number of permutations of s equals n! /(n In2.ngo) Proof: We can think of it this way. There are n places, and we want to put exactly one of the objects of s in each of the places. Since there are n au,s in s. we must choose a subset of n, places from the set of n places. C(n, n1) We next decided which places are to be occupied by the a2▪ Theorem 4.11: Let multiset S={n1 •a1 ,n2 •a2 ,…,nk •ak }, and n=n1+n2+…+nk=|S|. Then the number of permutations of S equals n!/(n1 !n2 !…nk !)。 ▪ Proof: We can think of it this way. There are n places, and we want to put exactly one of the objects of S in each of the places. ▪ Since there are n1 a1 ’s in S, we must choose a subset of n1 places from the set of n places. ▪ C(n,n1 ) ▪ We next decided which places are to be occupied by the a2 ’