This book provides a wide variety of mathematical problems for teenagers and students to help stimulate interest in mathematical ideas outside of the classroom. Problems in the text vary in difficulty from the easy to the unsolved, but all will encourage independent investigation, demonstrate different approaches to problem-solving, and illustrate some of the famous dilemmas that well-known mathematicians have attempted to solve. Helpful hints and detailed discussions of solutions are included, making this book a valuable resource for schools, student teachers, and college mathematics courses, as well as for anyone fascinated by mathematical ideas.