This book is a comprehensive guide to mathematical modeling. It uses classical models from the operations research as "case studies" and represents them as mathematical models. The models are coded in the computer language LPL and most can be solved directly over the Internet. The book contain many modeling tricks and teachers in Mathematics on high school will be amazed how playful and diverting mathematical modelling can be. The goal is to encourage the use of computer tools in an educational context in order to improve and develop mathematical modelling skills. It can be used as a self-study or in classes.