Lesson 6

Comparemos métodos de resta

Lesson Purpose

The purpose of this lesson is for students to compare methods for subtracting a one-digit number from a two-digit number with and without decomposing a ten.

Lesson Narrative

In the first activity, students consider 3 methods for finding the difference represented using base-ten diagrams. In the second activity, students find the difference with and without decomposing a ten and represent their thinking using base-ten diagrams, words, or equations. Students are not expected to draw their work with base-ten diagrams in a specific way. Students should have access to base-ten blocks throughout the lesson and the cool-down. Students compare their methods, and the teacher records student thinking using base-ten diagrams and equations in the activity synthesis. In the lesson synthesis, students consider different ways to represent decomposing.
• Representation

Learning Goals

Teacher Facing

• Describe how methods of subtraction are the same and different when subtracting a one-digit number from a two-digit number.

Student Facing

• Comparemos métodos de resta.

Required Materials

Materials to Gather

Materials to Copy

• Target Numbers Stage 4 Recording Sheet, Spanish

Required Preparation

Activity 2:

• Remove 0 and 10 from each set of cards (or prompt students to remove them) before the activity.

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

In upcoming lessons, students will subtract two-digit numbers from two-digit numbers with and without decomposing a ten. What do students need to understand about place value in order to use strategies that would require decomposing when subtracting by place?