Lecture 1
some of the class had trouble with seeing that the all coins would disappear when the minister picked coin 1 then 2 and so on, and you argued that there were 9 coins added every time to the urn. Well, this is where infinity is baffling, 9 times infinity is the same "kind" of infinity, that is there is a bijection between N (the set of natural numbers) and nine copies of N. Here's a numberphile video on the matter, see if it helps! Lastly, I highly recommend the chapter on Georg Cantor in the book Journey through Genius (the other chapters in the book are also highly recommended, just they are not related to our lecture).
Here's the biography of Girolamo Cardano.
Lecture 2