# Lesson 12

Comparemos problemas-historia de suma y de resta

### Lesson Purpose

The purpose of this lesson is to solve and compare Add To, Result Unknown and Take From, Result Unknown story problems.

### Lesson Narrative

In previous lessons, students solved Add To and Take From, Result Unknown story problems. The purpose of this lesson is to solve Add To, Result Unknown and Take From, Result Unknown story problems with the same context, which gives students an opportunity to focus on the action in each story and how it determines whether they need to add or subtract to solve the problem (MP2).

• Representation
• MLR8

### Learning Goals

Teacher Facing

• Compare addition and subtraction story problems.
• Solve Add To, Result Unknown and Take From, Result Unknown story problems.

### Student Facing

• Descubramos en qué se parecen y en qué son diferentes estos problemas-historia.

### Required Materials

Materials to Gather

### Required Preparation

Activity 3:

• Gather materials from:
• Bingo, Stages 1-3
• Math Fingers, Stages 1-3
• Math Stories, Stages 1 and 2
• Subtraction Towers, Stage 1
• 5-frames, Stages 1 and 2
• Counting Collections, Stage 1

### Lesson Timeline

 Warm-up 10 min Activity 1 10 min Activity 2 10 min Activity 3 20 min Lesson Synthesis 10 min Cool-down 0 min

### Teacher Reflection Questions

Think about a time you recently made a mistake during math class. How did you leverage your mistake to show students that mistakes are just learning in progress?