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Section 10-2. Using the Fundamental Counting Principle. Using the Fundamental Counting Principle. Uniformity and the Fundamental Counting Principle Factorials Arrangements of Objects. Uniformity Criterion for Multiple-Part Tasks.
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Section 10-2 • Using the Fundamental Counting Principle
Using the Fundamental Counting Principle • Uniformity and the Fundamental Counting Principle • Factorials • Arrangements of Objects
Uniformity Criterion for Multiple-Part Tasks A multiple-part task is said to satisfy the uniformity criterion if the number of choices for any particular part is the same no matter which choices were selected for the previous parts.
Fundamental Counting Principle When a task consists of k separate parts and satisfies the uniformity criterion, if the first part can be done in n1 ways, the second part can be done in n2 ways, and so on through the k th part, which can be done in nk ways, then the total number of ways to complete the task is given by the product
Example: Two-Digit Numbers How many two-digit numbers can be made from the set {0, 1, 2, 3, 4, 5}? (numbers can’t start with 0.) Solution There are 5(6) = 30 two-digit numbers.
Example: Two-Digit Numbers with Restrictions How many two-digit numbers that do not contain repeated digits can be made from the set {0, 1, 2, 3, 4, 5} ? Solution There are 6(5) = 30two-digit numbers.
Example: Two-Digit Numbers with Restrictions How many ways can you select two letters followed by three digits for an ID? Solution There are 26(26)(10)(10)(10) = 676,000 IDs possible.
Factorials For any counting number n, the product of all counting numbers from n down through 1 is called n factorial, and is denoted n!.
Factorial Formula For any counting number n, the quantity n factorial is given by
Example: Evaluate each expression. a) 4! b) (4 – 1)! c) Solution
Arrangements of Objects When finding the total number of ways to arrange a given number of distinct objects, we can use a factorial.
Arrangements of n Distinct Objects The total number of different ways to arrange n distinct objects is n!.
Example: Arranging Books How many ways can you line up 6 different books on a shelf? Solution The number of ways to arrange 6 distinct objects is 6! = 720.
Arrangements of n Objects Containing Look-Alikes The number of distinguishable arrangements of n objects, where one or more subsets consist of look-alikes (say n1 are of one kind, n2 are of another kind, …, and nk are of yet another kind), is given by
Example: Distinguishable Arrangements Determine the number of distinguishable arrangements of the letters of the word INITIALLY. Solution 9 letters total 3 I’s and 2 L’s