Cofman J. What to Solve. Problems and Suggestions for Young Mathematicians 1990

Textbook in PDF format

What to Solve? is a collection of mathematical problems for secondary school pupils interested in the subject. The arrangement of the text, the selection and grouping of the questions, the comments, references to related mathematical topics, and hints for further reading should illustrate my ideas about studying - or educating - through problem solving.
This book provides a wide variety of mathematical problems for teenagers and students to help stimulate interest in mathematical ideas outside of the classroom. Problems in the text vary in difficulty from the easy to the unsolved, but all will encourage independent investigation, demonstrate different approaches to problem-solving, and illustrate some of the famous dilemmas that well-known mathematicians have attempted to solve. Helpful hints and detailed discussions of solutions are included, making this book a valuable resource for schools, student teachers, and college mathematics courses, as well as for anyone fascinated by mathematical ideas.
Excellent book. Many excellent strategies for problem solving plus a chance to think about 100 mathematical problems, some quite easy, and some very hard. A great book for a Young Mathematician.
Problems for investigation
Approaches to problem solving
Problems based on famous topics in the history of mathematics
A selection of elementary problems treated by eminent twentieth-century mathematicians
Appendicies
Definitions and basic results
Notes on mathematicians mentioned in the text
Recommended reading
Index