Question

Use the permutation formula to solve a problem when n = 15 and r = 4.

Answer 1

The anwser is D .........

Answer 2

$nPr = \frac{n!}{(n - r)!}$

$15P4 = \frac{15!}{(15 - 4)!} = \frac{15!}{11!} \\ = \frac{15 \times 14 \times 13 \times 12 \times 11!}{11!} \\ 15 \times 14 \times 13 \times 12 = 32760$