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Learn about permutations and how to calculate different arrangements of objects in which order is important. Discover how to use factorials to find the number of possible arrangements and explore real-life examples.
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9-4 Permutations(pg 381-383) Indicator – D7
Permutation: an arrangement, or listing, of objects in which order is important (you can use the to find the # of possible arrangements) Ex: How many ways can 5 classes be arranged during 1st to 3rd period? 5P3 = FCP 5X4X3= 60
If the permutation includes all the members it can be written as a factorial – n! • (n members = n x (n-1) x (n-2)… × 1 or n!) • (Start at n and count backward until you get to 1, multiply all of those numbers.) Example: How many ways can you arrange12 students in a class picture? 12P12 = 12 × 11 × 10 × … × 1 or 12! = 479,001,600 ways!! Calculator Keys: 12 PRB > > ! = Screen Looks like: 12! Press = again.
You Try • There are 8 runners in a 5K race. How many different arrangements are there for the 1st , 2nd, and 3rd places • 8P3 • Answer: 8 × 7 × 6 = 336 different arrangements of winners
There are 5 students in line to board a bus. How many different ways could the students board the bus? • 5 P 5 • Answer: 5! = 120 different arrangements