I wrote a post that explains this as well, including a playable game with cards (uses js) https://www.michalpaszkiewicz.co.uk/blog/montyhallexplained/index.html

I wrote a post that explains this as well, including a playable game with cards (uses js) https://www.michalpaszkiewicz.co.uk/blog/montyhallexplained/index.html https://www.michalpaszkiewicz.co.uk/blog/montyhallexplained/...