unit 2: place value and multi-digit addition and subtraction
Unit 2 develops the concepts of grouping and ungrouping numbers as a key step in performing multi-digit addition and subtraction. The activities in this unit help students gain a practical understanding of addition and subtraction and the relationship between the two operations. Students are expected to apply their understanding of addition and subtraction to numeric calculations and real-world problem-solving situations, including those involving tables of data. Estimation and mental math provide students with a method to validate their answers.