Question 22202
I belive that this is problem involving combinatorics.So first you should ask does order matter? Does matter in what order you choose students? No, it does not - we will use combinationss (other option would be permutations),and can we repeatedly choose one student? Of course we can not, thus we are going to use combinations without repetition. Formula for that is {{{Cn = n!/((n-k)!*k!)}}}, where n is number od things you choose from and k is number of things you actually choose. In our case : {{{C15 = 15!/(9!*4!)}}} = 150150 , that is pretty many is it not ?