# Lesson 21

Solve Problems Using the Four Operations

### Lesson Purpose

The purpose of this lesson is for students to represent and solve two-step word problems using the four operations.

### Lesson Narrative

Previously, students have represented and solved two-step word problems using addition, subtraction, multiplication, and division with smaller numbers. In this lesson, students continue to deepen their understanding of two-step word problems as they consider what they need to know to solve problems and think about the relationship between numbers in a problem. Students write equations with a letter standing for the unknown quantity to represent these problems.

• Action and Expression
• MLR8

### Learning Goals

Teacher Facing

• Represent two-step word problems using equations with a letter standing for the unknown quantity.
• Solve two-step word problems using the four operations.

### Student Facing

• Let’s represent and solve problems using all four operations.

### 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

Check in with your norms and routines. Are they promoting engagement from all your students? Are there any adjustments you might make so that all students do math tomorrow?