Tworzymy kody czterocyfrowe spośród cyfr: $1$, $3$, $6$, $8$

$\underset{\begin{array}{c}\text{I}\\ \text{cyfra}\end{array}}{\underline{4}}\underset{\begin{array}{c}\text{II}\\ \text{cyfra}\end{array}}{\underline{3}}\underset{\begin{array}{c}\text{III}\\ \text{cyfra}\end{array}}{\underline{2}}\underset{\begin{array}{c}\text{IV}\\ \text{cyfra}\end{array}}{\underline{1}}$

$4\cdot 3\cdot 2\cdot 1=24$