The number of ways in which mn different items can be divided equally into m groups, each containing n objects and the order of the groups is NOT important is
(mn)!/(n!)m∗m!
Using formula, mn=9, m=3 groups n=3 objects (people):
(mn)!/(n!) m∗m != 9!/(3!)3∗3!'=
280
Answer: D(280)
