In this Grade 9 Saxon Algebra 1 lesson, students learn how to calculate the percent of change by dividing the amount of increase or decrease by the original amount and expressing the result as a percent. The lesson covers real-world applications including markups and discounts, where students find new prices after applying a percent of increase or decrease to an original cost. Part of Chapter 5 on Inequalities and Linear Systems, Lesson 47 builds percent reasoning skills through practical examples involving salaries, retail pricing, and fundraising totals.
Section 1
📘 Solving Problems Involving the Percent of Change
Algebra is a mathematical language that uses variables and symbols to represent unknown quantities, allowing us to model and solve complex, real-world problems.
To start, we'll apply these powerful ideas to a practical concept. You'll soon see worked examples and challenge problems on calculating the percent of change.
Section 2
Finding the Percent of Increase or Decrease
First, find the difference between the new and original numbers to find the amount of change. If the new number is bigger, you've got an increase! Then, just divide that change by the original amount and multiply by 100 to get your percentage. It's the perfect way to track growth or shrinkage in numbers!
Section 3
Application: Finding Markups and Discounts
A markup results when a percent of increase is applied to a cost. A discount results when a percent of decrease is applied to a cost.
New Price = Original Price + Markup
New Price = Original Price - Discount
Stores use markups to make a profit—they buy an item cheap and sell it for more! For you, a discount is awesome because it means a sale! You calculate the percentage of the original price and either add it (markup) or subtract it (discount) to find the final price. This is the math behind every price tag.
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Section 1
📘 Solving Problems Involving the Percent of Change
Algebra is a mathematical language that uses variables and symbols to represent unknown quantities, allowing us to model and solve complex, real-world problems.
To start, we'll apply these powerful ideas to a practical concept. You'll soon see worked examples and challenge problems on calculating the percent of change.
Section 2
Finding the Percent of Increase or Decrease
First, find the difference between the new and original numbers to find the amount of change. If the new number is bigger, you've got an increase! Then, just divide that change by the original amount and multiply by 100 to get your percentage. It's the perfect way to track growth or shrinkage in numbers!
Section 3
Application: Finding Markups and Discounts
A markup results when a percent of increase is applied to a cost. A discount results when a percent of decrease is applied to a cost.
New Price = Original Price + Markup
New Price = Original Price - Discount
Stores use markups to make a profit—they buy an item cheap and sell it for more! For you, a discount is awesome because it means a sale! You calculate the percentage of the original price and either add it (markup) or subtract it (discount) to find the final price. This is the math behind every price tag.
Book overview
Jump across lessons in the current chapter without opening the full course modal.
Continue this chapter