This Instructional Activity is a part of the Lesson 17, Unit 2, Grade 6. This activity asks students to choose or pose a Fermi problem and solve it, with the aim of promoting the reasoning and tools developed in this unit. Students brainstorm potential problems, choose one, and-after your review-use a graphic organizer to help them formulate the sub-questions that could support their problem solving. They go on to solve their chosen Fermi problem. To encourage ratio reasoning and the use of tools such as double number lines and tables, look for problems that involve two quantities. Questions that involve one quantity can be solved with multi-step multiplication and without ratio reasoning (e.g., "How many pens are there at the school?"