CSF10l14 - 11/8/10 Lecture 14 CS336 BasicCountingPrinciples...

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1 Lecture 14 CS336 Basics of Counting 1 Basic Counting Principles Product rule: Suppose that a procedure can be broken down into a sequence of two tasks where there are n 1 ways to do the first task and n 2 ways of doing the second, then there are n 1 n 2 ways to do the procedure. Sum rule: If a task can be done either in n 1 ways or n 2 way then there are n 1 +n 2 ways to do the task. Example A multiple-choice test contains 10 questions. There are 4 possible answers for each question. How many ways can a student answer the questions on the test if the student answers every question? How many ways can a student answer the test if the student can leave answers blank? Example How many different three-letter initials are there that begin with an A? Example How many bit strings are there of length 6 or less? Example How many strings of length eight English letters are there If letters can be repeated? if no letter can be repeated?
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This note was uploaded on 11/30/2010 for the course CS 336 taught by Professor Myers during the Fall '08 term at University of Texas at Austin.

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CSF10l14 - 11/8/10 Lecture 14 CS336 BasicCountingPrinciples...

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