Question

A boat is to be manned by eight men, of whom $2$ can only row on a bow side and $1$ can only row on stroke side; in how many ways can the crew be arranged?

Answer 1

2 men on the bow side can be choosen and arranged in ${}^4{P}_2=12$ ways

1 man on the stroke side can be choosen and arranged in ${}^4{P}_1=4$ ways

Remaining 5 men can be arranged in $5!$ ways

$\therefore$ Number of arrangements of the crew $=12\times 4\times 5!=5760$ ways