Using the combination formula, it is found that he can make 4 different stacks.
The order in which the balls are selected is not important, as stated in the problem. hence the combination formula is used to solve this question. If the order was important, then the permutation formula would be used.
[tex]C_{n,x}[/tex] is the number of different combinations of x objects from a set of n elements, given by:
[tex]C_{n,x} = \frac{n!}{x!(n-x)!}[/tex]
In this problem, he has four flavors, and will choose three of them for the stacks, hence the number of different stacks is given as follows:
[tex]C_{4,3} = \frac{4!}{3!1!} = 4[/tex]
He can make 4 different stacks.
More can be learned about the combination formula at https://brainly.com/question/25821700
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