Lesson 10
Decenas y decenas, unidades y unidades
Lesson Purpose
The purpose of this lesson is for students to add 2 two-digit numbers using methods based on place value.
Lesson Narrative
In the previous lesson, students added 2 two-digit numbers with composing a ten, in a way that made sense to them. This lesson focuses on adding tens and tens and ones and ones. This method is important because it sets students up to add multi-digit numbers in later grades. Students apply what they learned about the commutative and associative properties to see that it doesn’t matter if they add tens and tens first or ones and ones first.
- Representation
- MLR2
Learning Goals
Teacher Facing
- Add two-digit numbers by adding tens and tens and ones and ones.
Student Facing
- Sumemos números de dos dígitos.
Required Materials
Materials to Gather
Materials to Copy
- Number Puzzles Addition Stage 4 Gameboard, Spanish
Required Preparation
Activity 2:
- Create two separate posters that show base-ten drawings of 34 and 57. Leave space to write equations underneath the drawings.
Activity 3:
- Each group of 2 needs a set of digit cards from the previous center, Number Puzzles.
Lesson Timeline
| Warm-up | 10 min |
| Activity 1 | 10 min |
| Activity 2 | 15 min |
| Activity 3 | 15 min |
| Lesson Synthesis | 10 min |
| Cool-down | 0 min |
Teacher Reflection Questions
In what ways does the work of this lesson lay the foundation for student understanding of the standard algorithm for addition, which will be used in later grades?