Explanation

This is a combinatorics problem, and the WOW example is intended to make it clear that any W is considered identical to any other W—switching one W with another would not result in a
different combination, just as switching one S with another in MISSISSIPPI would not result in a different combination.

Therefore, solve this problem using the classic combinatorics formula for accounting for subgroups among which order does not matter:

$\frac{Total...number...of...items!}{First..group! \times Second...group!}$.

Because MISSISSIPPI has 11 letters, including 1 M, 4 S’s, 4 I’s, and 2 P’s:

$\frac{11!}{1! \times 4! \times 4! \times 2!}$

Now expand the factorials and cancel; use the calculator for the last step of the calculation: $34,650$.