Description Week 1 - (Two-digit) + (One-digit) and (Tens) + (Tens) Week 2 - (Two-digit) + (Two-digit) Week 3 - Challenge! Calculation Champion Week 4 - (Two-digit) - (One-digit) and (Tens) - (Tens) Week 5 - (Two-digit) - (Two-digit) Week 6 - Challenge! Calculation Champion Math Starts with Principles Math is an abstract discipline that expresses relationships between concrete objects through numbers and symbols. This is the main reason children find math difficult. Math can only show its true power when it is accompanied by proper understanding. At every stage, the underlying principles matter most. A Shift in Math Education The era of math education where simply knowing how to get the answer was enough is coming to an end. Rather than repeating a single method over and over, it's important for children to understand a variety of approaches to calculation. Textbooks teach why things work the way they do and encourage students to think of multiple methods, but when students only repeat simple drills, they forget the underlying principles and end up producing answers mechanically — leaving them without a solid understanding needed for applied problems. With Wonlisem, children can build steady calculation skills through a series of 4 to 6 books tailored to each stage of early childhood and elementary learning, studying for just 10 minutes a day. Principles and various problem-solving methods are introduced in a fun way with illustrations, practice is varied, and each unit wraps up with focused review. With this manageable daily study routine, children will find their calculation skills have grown remarkably before they know it. The revised edition of Wonlisem includes expanded video lectures and a strengthened curriculum for principle-based learning in the upper elementary grades, making it even easier for children to understand principles, concepts, and calculation methods, while reinforcing practice for a more complete learning experience. We hope Wonlisem can help resolve parents' concerns about their children's math practice.