Lesson objective: Fluently add multi-digit whole numbers using the standard algorithm.

This lesson helps to build procedural skill with the standard algorithm for addition. The vertical arrangement of addends is used here because it supports the concept of regrouping of place values. This work develops students' understanding that the standard algorithm is an efficient method of addition.

Students engage in Mathematical Practice 8 (Look for and express regularity in repeated reasoning) as they use the structure of the base-ten system to generalize application of the standard addition algorithm to larger numbers and more than two addends.

**Key vocabulary:**

- addend
- algorithm
- regroup