Problem 1. The following two parts are not related. Try them, to make sure you un- derstand the jargon of random variables distributions, probability density functions, etc. Ask your TA if you don't understand/remember what some phrase means. (a)Suppose X1, X2, and X3 are three mutually independent random variables, each having the uniform distribution

Notes for Recitation 14 Counting Rules Rule 1(Generalized Product Rule). Let be a set of length-k sequences. If there are: n1 possible first entries, n2 possible second entries for each first entry, n3 possible third entries for each combination of first and second entries, etc. then:

1 Sums and approximations Problem 1. Evaluate the following sums Solution. The formula for the sum of an infinite geometric series with ratio 1 /2

1 Graphs and Trees The following two definitions of a tree are equivalent Definition 1: A tree is an acyclic graph of n vertices that has n-1 edges Definition 2: A tree is a connected graph such that Vu, v E V, there is a unique path connecting u to u. In general, when we want to show the equivalence of two definitions, we must show

Notes for recitation 5 1 Well-ordering principle Every non-empty set of natural numbers has a minimum element Do you believe this statement? Seems obvious, right? Well, it is. But dont fail to realize how tight it is. Crucially, it talks about a non-empty set -otherwise, it would clearly be false. And it also talks about natural

Generating functions Generating functions are one of the most surprising, useful, and clever inventions in discrete math. Roughly speaking, generating functions transform problems about se- quences into problems about functions. This is great because weve got piles of mathe- matical machinery for manipulating functions. Thanks to generating functions, we can

Conditional Probability Suppose that we pick a random person in the world. Everyone has an equal chance of being selected. Let A be the event that the person is an MIT student, and let B be the event that the person lives in Cambridge. What are the probabilities of these events? Intuitively

Counting III Today we'll briefly review some facts you dervied in recitation on Friday and then turn to some applications of counting. 1 The Bookkeeper Rule In recitation you learned that the number of ways to rearrange the letters in the wore BOOKKEEPER is:

In this example, the domain is the set fa,b, c, d, el and the range is the set Y= (1, 2, 3, 4, 5/. Related elements are joined by an arrow. This relation is a function because every element on the left is related to exactly one element on the right. In graph-theoretic

Sums and Approximations When you analyze the running time of an algorithm, the probability some procedure succeeds, or the behavior of a load-balancing or communications scheme, you'll rarely get a simple answer. The world is not so kind. More likely, you'll end up with a complicated sum: