The goal of this lesson is for students to apply the formula for the sum of the first terms of a geometric sequence learned in the previous lesson. Students practice using the formula for the sum, , for both abstract and real-world situations, building fluency in its use and a greater understanding of the nature of geometric sequences, focusing on those with a common ratio greater than 1. In the last activity, students begin by making a prediction about the amount of yearly investment needed to reach $100,000 by the time they are 70. Students return to their prediction at the conclusion of the lesson as they make sense of the nature of geometric sequences and how they change (MP1). This context connects students back to the previous work they did with investments. Now students have new tools for analyzing more complex investment scenarios.

Technology isn't required for this lesson, but there are opportunities for students to choose to use appropriate technology to solve problems. We recommend making technology available.