00:02
Okay, so for this question we have five envelopes, which i'm going to represent as five dashes here, and five letters, which we'll just kind of think about holding in our hand.
00:12
And we want to know the probability that if we randomly put a letter in an envelope, what is the probability that we get all five of the correct letters in the correct envelopes? so we'll put a little c here, meaning that we've put the correct letter, first letter, in the first envelope.
00:29
So what's the probability that that happened? well, we had five letters total, and only one of them was the correct one.
00:37
So the probability that we picked the correct one would be one and five, right? well, after, let's assume that we did that.
00:44
We picked the correct one first.
00:45
Well, then what's the second letter? what's the probability that we get the correct one here? well, now we've got four letters, but since the correct one went into here, still only one of the letters is correct for this envelope...