See also the Dr. Math FAQ: Browse High School Discrete Math
Stars indicate particularly interesting answers or good places
to begin browsing. Selected answers to common questions: Four-
color map theorem. How many handshakes? Squares in a
checkerboard. - Contrapositive, Converse, Inverse [06/10/1999]
How can I write the contrapositive, converse, and inverse of and
prove or disprove the statement, "If m + n is even, then m and n
are even"? - Counting Rationals and Integers [10/06/1999] How
can you prove that the set of rational numbers is the same size
as the set of integers? - Determining the Winner of a Tennis
Match [10/9/1995] How many matches will it take to determine the
champion in a tennis tournament that started with 89 players? -
Finding and Factoring Large or Mersenne Primes [02/22/1998] How
do you find extremely large primes (Mersenne Primes) and how do
you tell if they are prime? What is the most efficient way of
factoring - Finding Primes: Sieve of Erastosthenes [4/1/1996]
Could you please elaborat