00:01
Well, this problem is when you're choosing 25 people at random.
00:03
We want to find the probability that no two of them will have the same birthday.
00:07
Now, the first person's not going to matter.
00:09
Let's just fix their birthday.
00:11
The first person's birthday is fixed.
00:14
Now, for the next person, that leaves 364 days out of a total of 365 for their birthday to be on.
00:27
The next person has 363 days out of a total of 365 because they can't have the same birthday.
00:35
Has the first one or the second one.
00:36
So that third person has 363 days to choose from.
00:40
The fourth person would be 362 over 365...