Marilyn Burns' Spaghetti
Of course, Marilyn Burns has the wonderful book, "Spaghetti and Meatballs for All!" but this is a different classic problem that she tweeted. If you break a piece of spaghetti at random, and the longer piece again at random, how likely is it that you can make a triangle.
Great problem for a visualization! I like that the simulation can support your intuition without giving you a theoretical probability.