# Lesson 7

¿Se forma una nueva decena?

### Lesson Purpose

The purpose of this lesson is for students to add one-digit numbers and two-digit numbers, and recognize when a new ten will be composed. They write equations to represent their addition methods.

### Lesson Narrative

In previous lessons, students added one-digit and two-digit numbers with composing a ten. They discussed methods that involved counting on, adding ones and ones then tens, and decomposing the one-digit number to make a new ten with the two-digit number.

In this lesson, students consider when a new ten will be composed before they find the value of a sum. When students recognize that they can compose a new unit of ten whenever the ones digits make 10 or more ones, they look for and make sense of the base-ten structure of numbers (MP7). Students write equations that represent their thinking.

• Action and Expression
• MLR6

### Learning Goals

Teacher Facing

• Add a one-digit and a two-digit number and recognize when a new ten will be composed.
• Write equations that represent addition methods.

### Student Facing

• Sumemos números de un dígito y de dos dígitos, y escribamos ecuaciones.

### 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

At what points during the lesson did you learn the most about your students’ thinking? How did you use what you learned during this lesson and how will you use what you learned in tomorrow’s lesson?