So in example number two, both of them should have been female. Now we want one girl and one boy. The question is what exactly is the probability? So let's take a look at the following diagram. The following pun and square to basically calculate what the probabilities are, first we actually have to apply the product rule. So let's say this is event number one and let's suppose that we have so this is our boy and girl and then we have boy and a girl.