Competency Based Mathematics for secondary schools Book1 is the first volume in a series of five Mathematics books "Competency Based Mathematics for secondary schools"Competency Based Mathematics for secondary schools is a secondary school Mathematics textbook series which consist of five volumes corresponding to each of the five classes in secondary school. The books are elaborated using the competency-based-approach from a situated perspective (through real life situations). This means that the target is to ensure that the learner possesses the know-how when faced with a daily life challenge or problem.At the end of each module, the learner is expected to have developed competencies which will enable him to use mathematics with confidence to solve some real life problems within a number of domains of life, communicate concisely and unambiguously and develop the power of mathematical reasoning.In book 1, the work covered in the primary schools is revised. Very little pre-knowledge is assumed and the teachers are advised to assume very little in other to close the gaps which might have been left in the primary schools. Throughout the course the learner and the teacher should not take anything for granted even if it appears to resemble what was treated in the previous class. This is because at every level new competencies are introduced and old ones are developed and consolidated in different ways.