Probabilty 6: Factorials, Permutations, Combinations and Counting.
Here we are introduced to the idea of arranging three books on a shelf (3! - factorial), arranging 3 books out of 10 ( 10 P 3 -permutation) and choosing 3 books out of 10 to take with us on a trip (10 C 3 - combination). Also a quick glance at pascal's triangle and the symmetry of combinations.