Today we learned how to assign numbers in the ordered sets (no repetition allowed).
So there are 2 ways of thinking of it：
Let's say we want to assign 2 people to be committees from a group of 5 people, how many sets of it?
Let's assume we the repetition is allowed, so there 25 ways (5*5) totally, then we minus 5, because in each lines there is one match repetition, and there 5 repetitions totally, so 25 - 5 = 20 ways.
The second way of thinking of it is there are 5 people, so there are 5 possibilities to assign the first person, then after one person deducted, there are four possibilities to assign the second person.
So it is 5 * 4 = 20
Also, there are 20 ways totally of assigning it.
