Math Mammoth Percent teaches students the concept of percent, percentage of a number, discounts, sales tax, percent of change, circle graphs, and percent of comparison. It is suitable for 6th-8th grades. The concept of percent builds on the students' understanding of fractions and decimals. Specifically, students should be familiar with the idea of finding a fractional part of a whole (such as finding 3/4 of $240). Assuming the student has mastered that, and can easily convert fractions to decimals, then studying the concept of percent should not be difficult. The first lesson, Percent, practices the concept of percent as a hundredth part, and how to write fractions and decimals as percentages. Next, we study how to find a percentage when the part and the whole are given (for example, if 15 out of 25 club members are girls, what percentage of them are girls?). The following two lessons have to do with finding a certain percentage of a given number or quantity. First, we study how to do that using mental math techniques. For example, students find 10% of $400 by dividing $400 by 10. Next, students find a percentage of a quantity using decimal multiplication, including using a calculator. For example, students find 17% of 45 km by multiplying 0.17 × 45 km. I prefer teaching students to calculate percentages of quantities using decimals, instead of using percent proportion or some other method. That is because using decimals is simpler: we simply change the percentage into a decimal, and multiply, instead of having to build a proportion or use fractions. Next is a lesson about discounts, which is an important application in everyday life. Then, we go on to the lesson Practice with Percent, which contrasts the two types of problems students have already studied: questions that ask for a certain percentage of a number (the percentage is given), and questions that ask for the percentage. The next major topic is the percentage of change. The concept of percentage of change deals with percentage increases and decreases in quantities (especially prices). Tying in with percentage of change, there is one lesson on Comparing Values Using Percentages. Simple Interest is a lesson on the important topic of interest, using as a context both loans and savings accounts. Students learn to use the formula I = prt in a great variety of problems and situations. The text concludes with a thorough review lesson of all of the concepts taught in the other lessons.