00:04
Okay, today's question is how many ways can an advisor choose four students from a class of 12 if they're all assigned the same task? so we are going to use combinations to answer this question because the order does not matter in this question because they're all doing the same task.
00:29
So we're going to do 12.
00:30
We're choosing out of 12 and we're picking four of them.
00:33
So we use our combination formula, which is going to be 12 factorial over 4 factorial, 12 minus 4 factorial.
00:51
So once we simplify that, we have 12 factorial over 4 factorial, 8 factorial.
01:03
Now what i would do to simplify is since 12 factorial means 12 times 11 times 10 and so on, and 8 factorial means 8 times 7, times 6, and so on.
01:14
We can cancel everything out from the 8 and down.
01:19
So that leaves us with on the top 12 times 11 times 10 times 9, and then the rest of that cancels out.
01:32
On the bottom, since i canceled out the 8 factorial, i still have the 4 factorial, which is 4 times 3 times 2 times 1.
01:43
Now i multiply that.
01:45
I get 1180 on the top and 24 on the bottom, which will divide to give me 495...
