The New Mexico Mathematics Contest for high-school students has been held annually since 1966. Each November, thousands of middle- and high-school students from all over New Mexico converge to battle with elementary but tricky math problems. The 200 highest-scoring students meet for the second round the following February at the University of New Mexico in Albuquerque where they listen to a prominent mathematician give a keynote lecture, have lunch, and then get down to round two, an even more challenging set of mathematical mind-twisters. Liong-shin Hahn was charged with the task of creating a new set of problems each year for the New Mexico Mathematics Contest, 1990-1999. In this volume, Hahn has collected the 138 best problems to appear in these contests over the last decades. They range from the simple to the highly challengingnone are trivial. The solutions contain many clever analyses and often display uncommon ingenuity. His questions are always interesting and relevant to teenage contestants. Young people training for competitions will not only learn a great deal of useful mathematics from this book but, and this is much more important, they will take a step toward learning to love mathematics.