Progressive Learning in O Level Mathematics is a series of four books specially written for students taking the O Level Mathematics syllabus 4048. It is essential for students to acquire and apply mathematical concepts and skills for progressive learning and to support learning in other subjects as well. When students develop their cognitive and metacognitive skills through mathematical problem solving, they would be able to achieve a desirable level of mastery in mathematical concepts. This would progressively build their confidence and foster interest in the subject. In addition, applications and modelling connect concepts to real-world situations. Through mathematical modelling, students solve problems in real-world contexts and reflect on the solution before interpreting it.