Lesson 14
Write and Solve Equations with Unknowns
Lesson Purpose
The purpose of this lesson is for students to relate equations to and write equations for multiplication situations and diagrams using a symbol for the unknown number.
Lesson Narrative
Students have worked with addition and subtraction equations with a symbol to represent the unknown number in grades 1 and 2. Students build on that work and the work with multiplication equations in the previous lesson as they encounter multiplication equations that have a symbol for the unknown number for the first time.
 Representation
 MLR8
Learning Goals
Teacher Facing
 Relate equations to multiplication situations and diagrams using a symbol for the unknown number.
 Write equations for multiplication situations and diagrams using a symbol for the unknown number.
Student Facing
 Let’s work with equations with unknown numbers.
Required Materials
Materials to Copy
 Card Sort Unknown Numbers
Required Preparation
Activity 1:
Lesson Timeline
Warmup  10 min 
Activity 1  15 min 
Activity 2  20 min 
Lesson Synthesis  10 min 
Cooldown  5 min 
Teacher Reflection Questions
How do tape diagrams help students make sense of equations in which the unknown number is in different positions?
Suggested Centers
 Capture Squares (1–3), Stage 5: Multiply with 2, 5, and 10 (Addressing)
 Five in a Row: Addition and Subtraction (1–2), Stage 8: Add within 1,000 with Composing (Supporting)
Print Formatted Materials
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Additional Resources
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