# Lesson 12

Restemos estratégicamente

### Lesson Purpose

The purpose of this lesson is for students to consider when they might use algorithms or other strategies to subtract.

### Lesson Narrative

Students have learned several subtraction algorithms in prior lessons. Now students take time to consider when it makes sense to use an algorithm and when it makes sense to use another strategy, such as those learned in grade 2. Students will consider how thinking about the numbers in the problem can help them use their knowledge of subtraction to flexibly subtract within 1,000.

• Engagement
• MLR8

### Learning Goals

Teacher Facing

• Subtract within 1,000 using algorithms or other strategies based on the numbers in the problem.

### Student Facing

• Pensemos en cuándo usar algoritmos y cuándo usar otras estrategias para restar.

### Required Materials

Materials to Gather

Materials to Copy

• Greatest Difference, Smallest Difference

### Required Preparation

Activity 2:

• Each group of 2 will need a paper clip.

Building Towards

### Lesson Timeline

 Warm-up 10 min Activity 1 20 min Activity 2 15 min Lesson Synthesis 10 min Cool-down 5 min

### Teacher Reflection Questions

Reflect on your experience with the Number Talks in the curriculum. What moves or questions have improved the learning for each of your students during this routine? What improvements would you make next time?