This textbook supports Tanzanian students in Form I. When Form I students start learning subjects in English, they often cannot use the language well enough to learn Mathematics effectively. Good teaching builds on students’ previous learning. For Form 1 students, their previous learning was in Kiswahili. This book is: • Language accessible. This means it is written in a simple way, with content communicated through diagrams and activities. • Language supportive. This means that the textbook helps students to develop the English that they need to learn Mathematics. It also means that the book helps Form I students to recall their mathematical knowledge from primary school and translate this into English. • Tanzanian. Mathematics is used in Tanzania on a daily basis. Mathematics was developed by men and women from different parts of the world in response to human needs, to solve problems and for fun. This book represents the multicultural background of Mathematics and its use in Tanzania. We think the result is a great book that will be easy for teachers and students to use. Above all, it will show students that learning Mathematics can be exciting, fun and useful. We hope you enjoy using the book as much as we enjoyed writing it.