1. Class 2, January 28, 2016 Lesson 5.2: Millions, Billions, or Trillions?

2.  By the end of this lesson, you should understand that: ◦ Keeping track of the number of zeros in large numbers is useful for rough estimations. ◦ There are huge differences between measures of a million, a billion, and a trillion. ◦ There are different ways to compare dollar amounts across large time spans.

3.  By the end of this lesson, you should be able to: ◦ Estimate the approximate size of the product of several large quantities. ◦ Use the Consumer Price Index and proportional reasoning to adjust dollar amounts for inflation. ◦ Compare the US national debt at various times in history by both (1) adjusting for inflation, and (2) expressing the debt as a percentage of the Gross Domestic Product.

4.  Main ideas in the lesson: ◦ It is important to understand the huge differences between millions, billions, and trillions. Estimation strategies such as keeping track of the number of zeros help us work with numbers of this magnitude. ◦ There are several ways to compare dollar amounts over time.

5.  Connections to the 8 course goals: 2. Reason abstractly and quantitatively. 6. Attend to precision. (Note that attending to precision means attending to an appropriate degree of precision: compute as accurately as necessary when a precise answer is required, but use estimation to get a good intuitive understanding of a problem.)