# Lesson 17

A Fermi Problem

### Lesson Narrative

This unit concludes with an opportunity for students to apply the reasoning developed so far to solve an unfamiliar, Fermi-type problem. Students must take a problem that is not well-posed and make assumptions and approximations to simplify the problem (MP4) so that it can be solved, which requires sense making and perseverance (MP1). To understand what the problem entails, students break down larger questions into more-manageable sub-questions. They need to make assumptions, plan an approach, and reason with the mathematics they know.

Engineers, computer scientists, physicists, and economists often make simplifying assumptions as they tackle complex problems involving mathematical modeling. Later in the year, unit 9 provides more exploration with solving Fermi problems, which are examples of mathematical modeling (MP4).

### Learning Goals

Teacher Facing

• Apply reasoning developed throughout this unit to an unfamiliar problem.
• Decide what information is needed to solve a real-world problem.
• Make simplifying assumptions about a real-world situation.

### Student Facing

Let’s solve a Fermi problem.

### Student Facing

• I can apply what I have learned about ratios and rates to solve a more complicated problem.
• I can decide what information I need to know to be able to solve a real-world problem about ratios and rates.

Building On