00:01
In this video, our objective is to find the number of different ways that an instructor can choose four students from a class of 11 students for a field trip.
00:09
So we can say that this is equals to 11c4.
00:16
All right.
00:19
So here it has been given that n is equal to 11 and r is equals to 4.
00:26
All right.
00:27
So here you can see that usually we use the combination form.
00:33
When only the number of possible groups are to be found, okay? and the sequence of arrangement is not needed.
00:42
Okay, so here we are using the combination formula.
00:45
So find out the number of phase.
00:48
So the usual combination formula is ncr is equal to n factorial upon r factorial times n minus r factorial.
01:07
Factorial, all right.
01:10
So let's plug in the values here.
01:12
So this is going to be equals to 11 factorial upon 4 factorial times 11 minus 4 factorial.
01:25
Okay, so let's solve this ahead.
01:27
Solving this ahead.
01:28
This is first let's subtract this...
