00:01
Okay, in this one we have that we have 65 % of people watch comedies, 55 % watch dramas, and 25 % watch neither.
00:09
And we want to know the probability that somebody watches comedies if we know that they watch drama.
00:14
So the first thing i'm going to do is i'm going to draw a venn diagram.
00:16
That's going to really help me to understand what we're looking at.
00:19
All right, so i'm going to call this circle c for comedies and this circle d for dramas.
00:25
All right.
00:26
So we know that 25 % watch neither.
00:28
So i'm going to put a big 25 % out here for neither comedies nor dramas.
00:33
And we know that 65 % watch comedies, and we know that 55 watch dramas.
00:39
What we don't know is right here.
00:41
But that's okay.
00:42
We can figure it out because the total is going to be 70.
00:44
The total of all of this universal set is going to be 100%.
00:48
So we know that this is going to be that minus 25.
00:51
So this has to equal 75%.
00:53
So what that tells us is that we can use this formula, the union of a and b...