Unit 3, Lesson 2
Addition and Subtraction Situations
Grade 3
Preparation
Lesson Narrative
Prior to this grade, students used various strategies and representations to solve problems involving addition and subtraction of multi-digit numbers (first within 100, and then within 1,000).
This lesson enables the teacher to see the strategies and representations that students use, which may include base-ten blocks or diagrams, number lines, or equations. It also elicits what students know about using place value to add or subtract (for instance, combining hundreds and hundreds, tens and tens, and ones and ones). The work here prepares students to learn algorithms for addition and subtraction, which also are grounded in the same ideas.
- Action and Expression
- MLR8
- Explain (orally) strategies for solving addition and subtraction problems within 1,000.
- Let’s solve problems involving addition and subtraction.
Required Materials
Activity 1
Required Preparation
None
Extend the Activity Synthesis of Activity 1, “Falls and Monuments,” by showing students the image of Iguazu Falls again and explaining that water continually moves on Earth between the oceans, rivers, lakes, the sky, and the land. That movement, powered by heat from the sun, is called the water cycle. Ask:
- “Why do you think the water cycle is important?” (All living things, including plants and animals, need water.)
- “What do you think would happen if there were no water cycle, or if it suddenly stopped?” (We’d run out of fresh water. All the water would end up in the ocean. There would be no clouds or rain or snow. Plants and animals would not have enough water to live.)
Environmental Principles & Concepts
Teacher Reflection Questions
What strategies did you anticipate that your students would use today? Which did you not anticipate?