here is another one. It rains in Las Vegas an average of 26 days a year. Even that is hard for me to believe. they must be counting days that it rains for 2 minutes.

But lets go with that number. That is a 7% chance it will rain tomorrow. But if you say what are the chances it rains yesterday, which has already occurred and it DID rain yesterday, then the chances are 100%. And that is what you are asking....what are the chances this event (past tense happened. Well it did happen so 100%.

And if you need proof try this. Look at the weather forecast someday. Maybe it says 50% chance of rain. Now as you are standing there in the rain, go back to that weather forecast for your location. It now says 100% chance of rain.