Permutations - part 1

Hey everybody, this is Irene, and our lesson on November 22nd was about Permutations.

The definition of "PERMUTATION" is a set of distinct objects in an arrangement of objects without any repetition in a specific order.

And to "PERMUTE" a set if objects means to rearrange them.

The formula we use for Permutation is:

nPr = n!

________

(n-r)!

Where:

n = total number of objects

r = number objects selected

Hint: n > r

( n; must always be positive.)

Ex #1: How many three letter "words" composed from the 26 letters in the alphabet are possible if . . .

a) NO repetitions are allowed?

Method 1; (can only use formula is NO repetitions are allowed)

n = 26; because you have 26 letters to choose from.
r = 3; because you're trying to make 3 letter words.

sol'n

Method 2: "dash method" (can apply in both no repetition and repetition situations)




B) Repetitions allowed:

SPECIAL NOTE:

(Understand)
Homework: Permutations, Combinations & Binomial Theorem Assignment

due TOMORROW!