The application of mathematical modelling to physical, economic, and social systems is growing rapidly. This book describes the more important techniques of mathematical modelling, and shows how to apply these techniques to a variety of problems. Each chapter covers a different mathematical technique, discusses the kinds of situations in which it is useful, and shows how to apply the technique to different fields. Examples are drawn from many subjects, including physics, chemistry, economics, demography, biology, medicine, ecology, traffic flow, and others.