*Half a Century of Pythagoras Magazine* is a selection of the best and most inspiring articles from this Dutch magazine for recreational mathematics. Founded in 1961 and still thriving today, *Pythagoras* has given generations of high school students in the Netherlands a perspective on the many branches of mathematics that are not taught in schools.

The book contains a mix of easy, yet original puzzles, more challenging–and at least as original–problems, as well as playful introductions to a plethora of subjects in algebra, geometry, topology, number theory and more. Concepts like the sudoku and the magic square are given a whole new dimension. One of the first editors was a personal friend of world famous Dutch graphic artist Maurits Escher, whose 'impossible objects' have been a recurring subject over the years. Articles about his work are part of a special section on 'Mathematics and Art'.

While many books on recreational mathematics rely heavily on 'folklore', a reservoir of ancient riddles and games that are being recycled over and over again, most of the puzzles and problems in *Half a Century of Pythagoras Magazine* are original, invented for this magazine by *Pythagoras'* many editors and authors over the years. Some are no more than cute little brainteasers which can be solved in a minute, others touch on profound mathematics and can keep the reader entranced indefinitely.

Smart high school students and anyone else with a sharp and inquisitive mind will find in this book a treasure trove which is rich enough to keep his or her mind engaged for many weeks and months.

Preface

1. Brainteasers

2. Puzzles, Games, and Strategies

3. Mathematics and Art

4. Geometry

5. Numbers

6. Dionigmas

7. Solutions

Bibliography

About the Editors

### About the Editors

Alex van den Brandhof (1976) completed his master’s degree in mathematics at VU University Amsterdam. Since 2001 he has been a mathematics teacher, first at a high school in Amsterdam and since 2011 in Basel (Switzerland). He was a member of the board of the Dutch Mathematical Olympiad. Since 2001 he has been coordinating editor of *Pythagoras* magazine. Furthermore, Alex van den Brandhof is a science journalist, writing about mathematics and computation for various media. He is one of the initiators of biographical dictionary of Dutch mathematicians. He wrote a book for high school students about probability theory and was one of the authors of a book about the seven millennium problems.

Jan Guichelaar (1945) studied mathematics, physics, and astronomy at the University of Amsterdam and got his master’s degree in theoretical physics in 1971. He got his PhD in 1974 on a thesis on relativistic kinetic gas theory. He worked as teacher and principal of a high school in Amsterdam. Later he taught at the faculty of mathematics and natural sciences of the University of Amsterdam. The last ten years of his career he was principal of a group of high schools in Amsterdam. Since his retirement in 2005 he has worked in the field of history of science and published as author and editor on astronomy and physics. He wrote a biography of the Dutch astronomer Willem de Sitter. Since 2001 he has been an editor of *Pythagoras* magazine.

Arnout Jaspers (1958) got a master’s degree in physics from Leiden University, and then changed course for a career in science journalism, specializing in mathematics, physics, astronomy and statistics. He was science editor at several newspapers and magazines. From 2006 until 2011, he was editor-in-chief of *Pythagoras* magazine. In 2012, he published *Het Labyrint van Occam* (*Occam’s Labyrinth*), a collection of his best, original math puzzles. He contributed to several other popular scientific books. He is now a freelance science writer, working mainly for public radio and several popular scientific websites.