00:01
In this question we are given there are 15 students and there are three cars to bring them downtown.
00:07
The first car can hold 6 person, second 5 and the third car can hold 4 person.
00:12
In part a, want to find a number of different ways the students can arrange themselves to get downtown.
00:17
So take note that the students selected for each car are without replacement.
00:25
After they are selected, they are not arranged in any particular order within the car they are selected for.
00:31
So the order selection is not important.
00:36
Without replacement order, not important.
00:38
We're using the concept of combination.
00:41
But since there are three cars, and we are to select the students and fit them into each of the three cars, so we're talking about multi -normal combination.
00:55
That is, if i have an distinct object, and i want to choose r one of them, and then later choose r2 of them are the remaining, and then later all the way to rk of them, from the remaining.
01:10
Then it will be n factorial divided by r1 factorial, r2 factorial all the way to rk factorial.
01:18
So in this case we have 15 students, we will select 6 for the first car, and then the remaining people select 5 for the second car and the remaining people select 4 for the third car...