Question

How do you evaluate `""_7P_4`?

Answer 1

840

Explanation:

The general formula for a permutation is:

`P_(n,k)=(n!)/((n-k)!)`; `n="population", k="picks"`

and so:

`P_(7,4)=(7!)/((7-4)!)=(7!)/(3!)=(7xx6xx5xx4xx3!)/(3!)=7xx6xx5xx4=840`