This is the first of four lessons about percent increase and percent decrease. The goal of this lesson is to understand what is meant by “20% more than” or “10% less than.” Students relate this language to the previous two lessons where they talked about “half as much again” and “one third less than.” They use tape diagrams to represent percent increase and percent decrease, and to solve problems. The contexts in this first lesson are all of the type where you are given the original amount and the percent increase or decrease and must calculate the final amount.