Question

Evaluate the expression: 18P4 A. 3,060 B. 12,240 C. 18,360 D. 73,440

Answer 1

$18P4=\dfrac{18!}{(18-4)!}=\dfrac{18!}{14!}=15\cdot16\cdot17\cdot18=73440$

Answer 2

$\bf _nP_r=\cfrac{n!}{(n-r)!}\qquad \qquad \qquad _{18}P_4=\cfrac{18!}{(18-4)!}$

one may note that, your calculator besides having a [ ! ] factorial button, it also has a [ ₙPᵣ ] button for permutations, and you can use that too.