This book presents a complete Learning Framework in Number (LFIN) across the primary grades K to 5. The LFIN provides a coherent overview of instruction in whole number arithmetic. It is organized into key domains of number from emergent numeracy through to strong additive and multiplicative arithmetic, which teachers can use to organize their assessment, planning, and instruction. For each student, learning number demands a progression of increasing conceptual sophistication, along with the development of a rich network of number relationships. Supporting most students with this learning requires a responsive, targeted, enquiry-based instruction over several years of schooling. The LFIN and the suite of pedagogical tools are designed to enable such responsive instruction.