Question

1. which formula is used to calculate the number of permutations of n items taken r at a time?

a. ( n! + r! )
b. ( \frac{n!}{(n - r)!} )
c. ( \frac{n!}{(n + r)!} )
d. ( \frac{n!}{r!} )

Explanation:

Step1: Recall permutation formula

The formula for permutations of \(n\) items taken \(r\) at a time is \(P(n,r)=\frac{n!}{(n - r)!}\).

Answer:

B. \(\frac{n!}{(n - r)!}\)