Perms and Coms

Yesterdays class, we learned more about perms and coms. Permulations are the number of possible orderings of a set, provided that the order of set elements matters. An example would be 281-0563 218-0563 560-3812 or books on a shelf, locker combos. The BEST EXAMPLE EVER of a perm, is create 5 letter words from the alphabet no repeats. So you pick any 5 letters, and then you would times 26(because there is 26 letters in the alphabet) then 25 because you used a letter, then 24 b/c you used another letter...etc. you get 7893 600. At that point we learned the formula : 26!/21!=n!/(n-r)! n being the number of items to select from and r being selecting items r at 2 time. "n things, permulated 5 at a time". The second part of THE BEST EXAMPLE EVER is: pizzas. you have peperoni pinapple and ham, either order you put it in, its still the same pizza.