Lesson 6

The Locker Problem

Lesson Purpose

The purpose of this lesson is for students to examine factors of numbers from 1 to 20 and use them to solve problems.

Lesson Narrative

In previous lessons, students used multiples to solve problems about equal-size groups (tables that accommodate certain numbers of seats and packages that contain certain numbers of items). In this lesson, students apply their knowledge of factors, multiples, prime numbers, and composite numbers to solve problems about a game involving opening and closing of lockers. Students look for patterns in the factors or multiples of numbers and use them to make predictions about the lockers that will have been touched after all 20 players of the game have a turn.

Math Community

Tell students they will reflect on the norms they identified at the end of this lesson.

  • Representation
  • MLR7

Activity 1: Questionable Lockers

Learning Goals

Teacher Facing

  • Apply understanding of factors, multiples, and prime and composite numbers to solve problems.

Student Facing

  • Let’s figure out what's happening in a game about lockers.

Required Materials

Required Preparation

CCSS Standards


Lesson Timeline

Warm-up 10 min
Activity 1 10 min
Activity 2 25 min
Lesson Synthesis 10 min
Cool-down 5 min

Teacher Reflection Questions

As students worked in their small groups today, whose ideas were heard, valued, and accepted? How can you adjust the group structure tomorrow to ensure each student’s ideas are a part of the collective learning?

Suggested Centers

  • Find the Number (4), Stage 2: Factors and Multiples (Addressing)
  • Five in a Row: Multiplication (3–5), Stage 2: Factors 1–9 (Addressing)
  • Secret Fraction (3), Stage 1: Building Non-Unit Fractions (Supporting)

Print Formatted Materials

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Additional Resources

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PowerPoint Slides

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