Question

which of the following is not a requirement of the permutations rule, $_np_r=\frac{n!}{(n - r)!}$, for items that are all different? choose the correct answer below a. order is taken into account (rearrangements of the same items are considered to be different) b. exactly r of the n items are selected (without replacement) c. there are n different items available. d. order is not taken into account (rearrangements of the same items are considered to be the same)

Explanation:

The permutations rule $_nP_r=\frac{n!}{(n - r)!}$ for distinct items requires that there are $n$ different items available, exactly $r$ of the $n$ items are selected without replacement, and order is taken into account. Order - being taken into account means rearrangements of the same items are considered different. Option D states that order is not taken into account, which is not a requirement of the permutations rule.

Answer:

D. Order is not taken into account (rearrangements of the same items are considered to be the same)