Progress in Mathematics is a five year secondary school course leading to the GCSE examination and closely linked to the National Criteria for Mathematics and the syllabuses of the GCSE examining groups. It emphasizes problem-solving and investigations, and forges links with other subjects. This pupils' text book is at the extension level, and therefore aimed at the most able fourth year secondary students. Like all the pupils' books, it caters for mixed-ability groups and recognizes the importance of flexibility. There are a minimum of textual explanations, so that teachers are free to choose their own teaching methods. The order in which new topics are introduced reflects the inbuilt spiralling of the curriculum, and the concise format minimizes organizational difficulties. Books of mental tests, answer books and copy masters are also available.