Counting Principles and Tree Diagrams

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# Counting Principles and Tree Diagrams - PowerPoint PPT Presentation

Counting Principles and Tree Diagrams. Fundamental counting principle. The Fundamental C ounting Principle states that if there are x ways to choose a first item and y ways to choose a second item, then there are x(y) ways to choose all items. . For example.

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## PowerPoint Slideshow about ' Counting Principles and Tree Diagrams' - todd

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Presentation Transcript
Fundamental counting principle
• The Fundamental Counting Principle states that if there are x ways to choose a first item and y ways to choose a second item, then there are x(y) ways to choose all items.
For example
• A telephone company is assigned a new area code and can issue new 7-digit phone numbers. All phone numbers are equally likely.
• Find the number of possible 7-digit phone numbers
• Use the Fundamental Counting Principle:
• 1st digit 2nd digit 3rd digit 4th digit 5th digit 6th digit 7th digit
• ? ?? ?? ? ?
• 10 10101010 10 10
• There are 10 choices for each digit (0-9), so there are
• 10(10)(10)(10)(10)(10)(10) = 10,000,000 phone number options
You try
• A telephone company is assigned a new area code and can issue new 7-digit phone numbers. All phone numbers are equally likely.
• Find the probability of a phone number that does not contain an 8.
• First, use the fundamental counting principle to find the number of phone numbers that do not contain an 8.
• 9(9)(9)(9)(9)(9)(9) = 4,782,969
• P(no 8) = 4,782,969 = .478
• 10,000,000
Using a tree diagram
• The Fundamental Counting Principle tells you only the number of outcomes in some experiments, not what the outcomes are. A tree diagram is a way to show all possible outcomes.
• For example:
• A pizza place specializes in two types of crust, sesame and plain, and sells five different toppings, onions, olives, ham, green peppers, and mushrooms. Create a tree diagram to show the options assuming there is only one type of crust with one topping.
Tree diagrams
• Using the Fundamental Counting Principle, we know that we should have 10 options: 2 pizza crusts, 5 toppings…2(5)=10
You try
• You are going on a trip. You can pack 2 pairs of pants, 3 shirts, and 2 sweaters for your vacation. Use a tree diagram to show all outfit options you can make if each outfit consists of a pair of pants, a shirt, and a sweater.
• There are 12 total outfits to choose from
• 2(3)(2) = 12