Lesson 18
Standard Algorithm to Add and Subtract
Lesson Purpose
The purpose of this lesson is to add and subtract large numbers within 100,000 using the standard algorithm.
Lesson Narrative
In grade 3, students found sums and differences within 1,000. Students analyzed and used different algorithms based on place value, including the standard algorithm. As students work with larger numbers in grade 4, they recognize that the standard algorithm is a reliable and efficient way to add and subtract within 1,000,000.
Grid paper should be made available but not required, as a tool to support aligning digits when adding and subtracting in each activity.
- Representation
- MLR2
Learning Goals
Teacher Facing
- Add multi-digit numbers, with composing, using the standard algorithm.
- Subtract multi-digit numbers, without decomposing, using the standard algorithm.
Student Facing
- Let’s find sums and differences of large numbers.
Required Materials
Materials to Gather
Required Preparation
CCSS Standards
Addressing
Lesson Timeline
| Warm-up | 10 min |
| Activity 1 | 15 min |
| Activity 2 | 20 min |
| Lesson Synthesis | 10 min |
| Cool-down | 5 min |
Teacher Reflection Questions
What strategies from earlier grades did students rely on to find sums and differences in the warm-up and first activity, before the standard algorithm was explicitly mentioned? How can you support students in connecting these strategies to the standard algorithm?
Suggested Centers
- Tic Tac Round (3–5), Stage 2: Any Place (Addressing)
- Number Puzzles: Addition and Subtraction (1–4), Stage 6: Beyond 1,000 (Addressing)