# Lesson 13

Resolvamos problemas de grupos iguales

### Lesson Purpose

The purpose of this lesson is for students to solve problems involving multiplication within 100, where one factor is a teen number, in a way that makes sense to them.

### Lesson Narrative

The work of this lesson connects to previous work because students have used strategies to multiply one-digit factors. Now, they have the opportunity to extend these strategies to the multiplication of teen numbers. Students may use area diagrams and expressions to represent multiplication strategies, which they used in the previous section. Students solve problems involving the multiplication of teen numbers, then make a poster of their work with a student who solved in a similar way. During the gallery walk, students see a variety of ways to represent and solve the problem (MP2). This will be helpful in the next lesson where students make sense of specific representations of multiplying within 100 when one factor is a teen number.

• Engagement
• MLR7

### Learning Goals

Teacher Facing

• Multiply within 100, where one factor is a teen number, in a way that makes sense to them.

### Student Facing

• Multipliquemos algunos números del 11 al 19.

### Required Materials

Materials to Gather

Materials to Copy

• Centimeter Grid Paper - Standard

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

Which students had opportunities to share their diagrams and thinking during whole-class discussion? How did you select these students?

### Suggested Centers

• Compare (1–5), Stage 2: Add and Subtract within 20 (Supporting)
• How Close? (1–5), Stage 4: Add to 1,000 (Supporting)