Math 120 SP08 Section 6.4 Notes: Permutations & Combinations Brodnick Example : 1. At the state track meet, 8 runners make it to their event final. If ribbons will be awarded for each place, how many ways can this be done? * An ordered arrangement of items is called a permutation of those items. * # of possible permutations of n items is n ! * in your calculator: # n MATH PRB 4:! Examples : 2. How many different ways can 7 people be seated in a row of chairs? 3. At the Olympics, only the top 3 finishers receive medals. If there are 7 finalists, how many ways can the medals be awarded? * A permutation of n items taken r at a time is an ordered list of r of the items chosen from a set of n items * Denoted n P r * in your calculator: # n MATH PRB 2: nPr # r Example : 4. 5 people apply for a $500 scholarship. If the scholarship committee selects 2 people, how many ways can the scholarship be awarded? * An unordered set of n items chosen r at a time is called a combination of those items.
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