MATHEMATICAL EXCURSIONS, Fourth 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 one understands that prime numbers are connected to credit card transactions; that compound interest is connected to student loans; and that the perils of radioactive waste take on new meaning when one understands exponential functions are connected to the disasters at Fukushima, Japan. 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. These are just a few of the facets of mathematics you will explore with this text. MATHEMATICAL EXCURSIONS will expand the way you know, perceive, and comprehend the world around you. Enjoy the journey!