Read more about the purpose of the MAP Classroom Challenges

Estimations and Approximations: The Money Munchers

Mathematical goals

This lesson unit is intended to help you assess how well students are able to:

  • Model a situation.
  • Make sensible, realistic assumptions and estimates.
  • Use assumptions and estimates to create a chain of reasoning, in order to solve a practical problem.


In this unit, students choose and use mathematics to model a problem situation.

  • Before the lesson, students attempt the task The Money Munchers individually. You then review their work and create questions for them to answer in order to improve their solutions.
  • At the start of the lesson, students again work individually on The Money Munchers task, answering your questions.
  • Next, students work collaboratively in small groups. Their task is to produce a better solution to The Money Munchers than they did individually. Then, working in the same small groups, students analyze responses to The Money Munchers written by students in another class.
  • In a whole-class discussion, students compare and evaluate the solution methods they have seen and used.
  • In the final part of the lesson, students spend ten minutes reviewing their individual solutions, and writing about what they have learned.

Materials required

  • Each student will need a copy of the task sheet The Money Munchers.
  • Each small group of students will need a new copy of the task sheet The Money Munchers, a sheet of poster paper, and a copy of the Sample Student Responses.
  • Provide calculators for students who choose to use them.
  • There are some projector resources to support whole-class discussion, and to help introduce activities.

Time needed

15 minutes before the lesson and a 1-hour lesson. Timings given are approximate and will depend on the needs of your class.

Mathematical Practices

This lesson involves a range of mathematical practices from the standards, with emphasis on:

Mathematical Content

This lesson asks students to select and apply mathematical content from across the grades, including the content standards:


Lesson (complete)

Projector Resources

A draft Brief Guide for teachers and administrators (PDF) is now available, and is recommended for anybody using the MAP Classroom Challenges for the first time.

We have assigned lessons to grades based on the Common Core State Standards for Mathematical Content. During this transition period, you should use your judgement as to where they fit in your current course.

The Beta versions of the MAP Lesson Units may be distributed, unmodified, under the Creative Commons Attribution, Non-commercial, No Derivatives License 3.0. All other rights reserved. Please send any enquiries about commercial use or derived works to

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