The book has been written to meet the growing requirements of candidates appearing for UPSC, SSC, Public Sector Examinations, Bank (PO), MBA Entrance Exams, Railways and Campus Placements of Software Companies etc. The comprehensive volume would enable the readers to acquire complete and detailed understanding of "Reasoning & Aptitude". It covers all dimensions of Arithmetic, Algebra, Geometry, Reasoning and Data Interpretation. My first-hand experience of coaching the students has been a great source of inspiration and has helped me immensely in writing this book. Preparation for Civil Services Examination taking Mathematics as optional subject also helped me sharpen the ideas and arguments developed here.