MATHEMATICAL EXCURSIONS, Third Edition, teaches you that mathematics is a system of knowing and understanding our surroundings. For example, sending information across the Internet is better understood when you understand prime numbers; the perils of radioactive waste take on new meaning when you understand exponential functions; and the efficiency of the flow of traffic through an intersection is more interesting after seeing the system of traffic lights represented in a mathematical form. You will learn those facets of mathematics that strengthen your quantitative understanding and expand the way you know, perceive, and comprehend your world. We hope you enjoy the journey.