6-4 - 6-4 Permutations and = n ×(n-1 ×(n – 2 ×… ×2...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 6-4 Permutations and CombinationsFACTORIALn! = n ×(n-1) ×(n – 2) ×… ×2 ×1e.g., 4! = 4 ×3 ×2 ×1Note: 4! = 4 ×3! In general, n! = n ×(n – 1)!Permutation: •a selection of a pre-specified number of items from a given set of items, where•different orderings of the same items are considered to bedifferent selections (and are counted separately)Example: set of items = {red, orange, yellow, green}some permutations, selecting 3 at a time:(red, orange, yellow)(orange, red, yellow)(yellow, green, red)(green, yellow, orange)•are there any more? how many are there in all?•you don’t need to list them all and then count themHere’s a formula (based on the multiplication principle):The number of permutationsof nthings taken rat a time is denoted by nPr, or Pn,rand the formula is:nPr= n ×(n - 1) ×(n-2)…(for rfactors)(formula different from book’s but equivalent and easier to use)To answer the above question:The number of permutations of 4 things taken 3 at a time:4P3= 4×3×2 = 246-4p. 1Combination...
View Full Document

{[ snackBarMessage ]}

Page1 / 3

6-4 - 6-4 Permutations and = n ×(n-1 ×(n – 2 ×… ×2...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online