ⁿPᵣ equals:
An! / (r! (n − r)!)
Bn! / r!
Cn! / (n − r)!
Dn × r
Answer & Solution
Correct answer: C. n! / (n − r)!
A permutation is an ordered arrangement of a set of objects. The notation $^nP_r$ (or $P(n, r)$) represents the number of ways to choose and arrange $r$ distinct items from a set of $n$ distinct items where the order of selection matters.
### Step-by-Step Derivation:
1. **First Position:** There are $n$ possible choices.
2. **Second Position:** Since one item is already used, there are $(n-1)$ choices.
3. **$r$-th Position:** Following the pattern, the $r$-th position has $(n - r + 1)$ choices.
### Mathematical Expression:
By the Fundamental Counting Principle, the total number of permutations is:
$$^nP_r = n \times (n - 1) \times (n - 2) \times \dots \times (n - r + 1)$$
To simplify this into factorial notation, we multiply and divide by $(n - r)!$:
$$^nP_r = \frac{n \times (n - 1) \times \dots \times (n - r + 1) \times (n - r) \times (n - r - 1) \times \dots \times 1}{(n - r) \times (n - r - 1) \times \dots \times 1}$$
This simplifies to:
$$^nP_r = \frac{n!}{(n - r)!}$$
Comparing this with the given options, the correct choice is **C**.
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