1. Class 9, October 1, 2015 Lessons 2.1 & 2.2

2.  By the end of this lesson, you should understand that: ◦ Population density is a ratio of the number of people per unit area ◦ Proportionality can be used to compare population densities

3.  By the end of this lesson, you should be able to: ◦ Calculate population densities ◦ Determine if two population density ratios are proportional to each other ◦ Compare and contrast populations via their densities

4.  Main idea: ◦ We can compare and contrast populations using population densities  Module 1 focused on percentages, with an introduction to ratios in Lesson 1.6. In this lesson, we developed more understanding of ratios, and specifically working with unit rates (a ratio with a denominator of 1).  Both percentages and ratios are a comparison of two numbers by division.  Units tend to be more important with ratios. (50 miles per hour is very different from 50 miles per minute!)

5.  By the end of this lesson, you should understand: ◦ The concept of proportional representation in voting ◦ How representation in the U.S. congress is allocated

6.  By the end of this lesson, you should be able to: ◦ Calculate a unit rate ◦ Solve a proportion by first finding a unit rate, and then multiplying appropriately

7.  Main idea: ◦ Rates and proportional reasoning can be used to assess election results