Answer:
There are 2,520 unique permutations.
Step-by-step explanation:
When we have a set of N different elements, the total number of permutations is given by:
P = N! = N*(N - 1)*(N - 2)*...*(2)*(1)
Particularly, if out of these N elements, there are a given element that is repeated K times, then the permutations of these K elements actually do not add new unique permutations, then in that case the total number of unique permutations is:
P = N!/K!
And if we have another element that is repeated L times, then with the same reasoning than above, the total number of unique permutations is:
P = N!/(K!*L!)
Now, we have the set:
{C, E, A, S, E, L, E, S, S}
So we have a set of 9 letters, then:
N = 9
And, the letter S is repeated 3 times
The letter E is repeated 3 times
Then, using the above notation, we can define:
K = 3
L = 3
The total number of permutations is then:
So there are 2,520 unique permutations.