This event is the first time around we get heads, the second time around we get tail. So we have an H and we have a T. This is a T and an H and finally we have a T and a T. Okay, now what about the probabilities? Well, one two times one two. So we have one half times one two gives us one four and we have one half. So once again we have one fourth and we have one four. And this makes sense because if we sum up these four values it has to add up to one or 100%.