n this book, children progress to two-digit addition while learning the commutative property of addition- an important foundation for future math success. Problems incorporate both horizontal and vertical form addition, which prepares children for practice with three and four-digit addition. Upon completion, your child will be ready for advanced arithmetic! Topics Covered in this Book: Horizontal addition review Vertical form addition Two-digit plus two-digit addition to 198 Early three- & four-digit addition Addition of three two-digit numbers Commutative property of addition Patterns & sequencing