MATHEMATICAL EXCURSIONS, Fourth Edition, teaches students that mathematics is a system of knowing and understanding our surroundings, and explores a selection of topics from various areas in mathematics. The topics were chosen to exemplify the power and diversity of mathematics and to connect math concepts to contemporary applications. For example, sending information across the Internet is better understood when one understands prime numbers; the perils of radioactive waste take on new meaning when one understands 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. Now fully supported by two strong digital learning solutions, Enhanced WebAssign and MindTap Math, students will learn those facets of mathematics that strengthen their quantitative understanding and expand the way they know, perceive, and comprehend their world.