probability
posted by Sharon .
How many different ways can 5 people be seated on a bench?

Assuming there are 5 places on the bench, and you place the people one seat at a time.
Number of people available for first seat = 5
Number of people available for second seat = 4
....
Number of people available for the last seat = 1
Total number of arrangements = 5! = 5.4.3.2.1 
120