How many ways can two letters be selected from five distinct letters when order matters?

When selecting two letters from five distinct letters where the order of selection matters, the result is a permutation. In combinatorics, this is denoted as ${}_n{P}_k$, where $n=5$ and $k=2$.

The number of ways to perform this selection is calculated using the formula:
$${}_n{P}_k=\frac{n!}{(n-k)!}$$

Substituting the values:
$${}_5{P}_2=\frac{5!}{(5-2)!}=\frac{5\times 4\times 3\times 2\times 1}{3\times 2\times 1}=5\times 4=20$$

There are 20 possible ways to select two letters from five when order is considered.1