Unit 2, Lesson 1
Add and Subtract to Compare
Grade 2
Preparation
Lesson Narrative
Up to this point, students have only subtracted multiples of 10 from other two-digit numbers within 100. In this lesson, students build on their work with interpreting bar graphs and solving Compare story problems to add and subtract within 100 with greater numbers. The representations given in both activities (bar graphs and connecting cubes) invite students to use and connect a variety of different methods and prepare students for using subtraction methods based on place value.
- Engagement
None
- Compare and contrast (orally) strategies for finding an unknown difference that involve addition and subtraction.
- Explain (orally) strategies for solving problems within 100 that do not involve composing or decomposing a ten.
- Let’s solve Compare problems with greater numbers.
Required Materials
Required Preparation
- Create towers of 10 with the connecting cubes.
- Have single connecting cubes available.
- Create towers of 10 with the connecting cubes.
- Have single connecting cubes available.
Teacher Reflection Questions
In grade 1, students used connecting cubes to understand a ten as a group of 10 ones. How did using the connecting cubes in today’s lesson help students consider strategies based on place value when adding or subtracting?