posted by phil .
how many can 5 people be arranged in a row if the father is on the far right?
Assuming the father is one of the five people, so that leaves us with only four to choose from for 4 places.
The first place can be filled with 4 choices, the second with 3, and so on.
So the number of arrangements is
4*3*2*1=4! with the father always on the right.