00:01
So in this question, we are going to use the base theorem.
00:04
So let's let a be the event that the queen is a carrier.
00:11
So queen is a carrier.
00:18
And let's let b be the event that she had three princes without the disease.
00:30
And what we want to find is the probability of a given b.
00:37
So we know that the probability of a, we know the probability of a is 0 .5.
00:46
That's given in the question.
00:49
So we can go ahead and actually find the opposite of this.
00:52
We find the probability of b given a.
00:56
And that's going to be 0 .5 times 0 .5 times 0 .5 since there are three princes.
01:02
And that gives us an answer of 0 .125.
01:05
Now we can find the probability of b.
01:10
So the probability of b is going to be equal to the probability of b given a, which we just got, times the probability of a, which we know, times, or plus the probability of b given not a, times the probability of not a.
01:32
And we can plug in what we have...