00:01
A family is chosen at random from the set of all families with exactly three children.
00:04
We need to find certain probabilities.
00:06
So first of all, consider all of the possible outcomes.
00:10
So the first child will either be a boy or a girl.
00:14
The second child will either be a boy or a girl.
00:19
And the third child will either be a boy or a girl.
00:27
So using this tree diagram, we can find out all of the possible outcomes.
00:31
The first one will be bb and the next one will be bbg and we can write the rest of the outcomes like this.
00:41
So we have bgb, bgg, gb, gb, gb, gb, gb, gb, gb, gb, and gdd.
00:56
So let's find the probabilities.
00:58
First of all, we need to find the probability that the family of three girls if it is known that one child is a boy.
01:03
So that will be the number of favorable outcomes divided by the total number of outcomes.
01:08
So the total number of outcomes, those will be all of the outcomes in which there is at least one boy, because one child, at least one child, is a boy...