In Topic B, students create algebraic representations and apply their understanding of percent from Topic A to interpret and solve multi-step word problems related to markups or markdowns, simple interest, sales tax, commissions, fees, and percent error (**7.RP.A.3**,** 7.EE.B.3**). They apply their understanding of proportional relationships from Module 1, creating an equation, graph, or table to model a tax or commission rate that is represented as a percent (**7.RP.A.1**, **7.RP.A.2**). Students solve problems related to changing percents and use their understanding of percent and proportional relationships to solve the following: *A soccer league has 300 players, 60%** of whom are boys. If some of the boys switch to baseball, leaving only 52% **of the soccer players as boys, how many players remain in the soccer league? *Students determine that, initially, 100% = 60% = 40% of the players are girls and 40% of 300 equals 120. Then, after some boys switched to baseball, 100% - 52% of the soccer players are girls, so 0.48*p* = 120, or *p* = 120/0.48. Therefore, there are now 250 players in the soccer league.

In Topic B, students also apply their understanding of absolute value from Module 2 (**7.NS.A.1b**) when solving percent error problems. To determine the percent error for an estimated concert attendance of 5,000 people, when actually 6,372 people attended, students calculate the percent error as:

(|5000 - 6372|)/|6372|, which is about 21.5%.