Final answer:
The permutation formula involving indistinguishable items is A) n! / (n1! * n2! * ... * nk!), where 'n' is the total number of items and 'n1, n2, ..., nk' are the numbers of items that are identical.
Step-by-step explanation:
The permutation formula for a problem with some indistinguishable items is given by the equation A) n! / (n1! * n2! * ... * nk!). Here, 'n' represents the total number of items to arrange, and 'n1, n2, ..., nk' represent the numbers of indistinguishable items of each type. To calculate permutations with indistinguishable items, you divide the factorial of the total number of items by the product of the factorials of each group of indistinguishable items. For example, if you have a total of 10 items wherein there are 4 items of one type and 3 items of another type (with the rest being unique), the number of distinct permutations would be calculated as 10! / (4! * 3!).