Analysis of Plinko!
Why did that happen yesterday? Remembering what we briefly mentioned about pathes on the first day, we see that at each nail, the Plinko disk could fall down either to the left or right. one accumulated set of left-right choices determines a path down the grid. The more paths there are leading to a pocket, the more likely it is that a disk will fall to that pocket. We note that the adding formula for Pascal's triangle can be interpreted as a way to count up the paths down the triangle, like falling disks in Plinko.
Define the factorial symbol: "!". Define permutations and combinations, and how these mathematical objects help us count the ways to define a path down the triangle, by "choosing" the number of left and right turns in a path of a certain length.
Homework: Practice calculation permutations and combinations, brainstorm applications of formula. Invent and solve 10 permutation and combination problems. (Sample answers: Choosing a baseball team starting lineup, dealing a hand from a deck of cards, choosing classes in school, elections, counting male/female distribution in families.)