This third edition of T eaching Mathematics for the 21st Century continues to help teachers let the secret out-to open up to their students the wonderful discoveries and challenges of the pattern-making and problem-solving aspects of a  fascinating subject: mathematics. The rationale remains the same-to enable prospective and current teachers to access and use tools and strategies to effectively teach mathematics to contemporary students. Changing demographics, knowledge of how people learn, and technology all impact the way we educate our young people.   This edition incorporates lessons and strategies from programs that have proven success in many types of classrooms. Many of these examples help students connect mathematics to real life situations and communicate their understanding of the underlying concepts. Although technology is constantly being upgraded, ways to increase student motivation through its application remains a goal. For example--since applets can enhance a lesson whether the teacher uses a computer projector, a "smart" board, or has students work individually on computers--we have identified several sources of mathematics applets that can be correlated to various lessons. Research citations and summaries have been updated to reflect current information on teaching and learning. For future teachers.