Money Math · Lesson Plan

Percent of Decrease

When a price drops — a sale, a markdown, a falling value — the percent of decrease describes how much it went down. This lesson teaches students to find the difference between the original and new price, write it as a ratio over the original amount, convert to a decimal and then a percent, and round when needed. Students practice on ten markdown scenarios.

Grades 6–9 Lesson Plan 30–45 minutes Free Lesson Plan Lesson & Worksheet: Full Membership

For Teachers

Lesson at a glance

Topic: Money Math
Grade Level: Grades 6–9
Resource Type: Lesson + Worksheet
Estimated Time: 30–45 minutes
Format: Lesson + worksheet + answer key
Materials: Printable lesson, worksheet, answer key, calculator

What Students Learn

Learning objectives

Define percent of decrease
Find the difference between an original and a lower new price
Write the decrease as a ratio over the original amount
Convert the ratio to a decimal and then a percent
Round a percent to the nearest whole percent when appropriate

Materials

What you’ll need

Printed copies of the lesson and worksheet (one per student)
Calculators
Pencils
Whiteboard or projector for worked examples

Key Terms

Vocabulary

Percent of decrease: The percent by which a price or amount has gone down over time.
Original amount: The starting price before the change.
New amount: The lower price after the change.
Difference: The result of subtracting the new price from the original price.
Ratio: A comparison of two numbers, often written as a fraction.
Rounding: Adjusting a number to a given place value.

For Teachers

Lesson plan

Estimated time: one 30–45 minute class period.

Lesson sequence

Introduction (5 min). Use the $40 → $35 example: by what percent did the price drop?
Teach the method (12 min). Find the difference, write it over the original amount, divide to a decimal, convert to a percent, and round when needed (e.g., 12.5% or 13%).
Worksheet (15 min). Students find the percent of decrease for ten original/new price pairs, rounding when necessary.
Review (8 min). Check answers with the answer key and connect to sales and markdowns.

Assessment

Assess the completed worksheet against the included answer key.

Discussion

Discussion questions

What does a percent of decrease tell you about a price?
How is finding a percent of decrease similar to finding a percent of increase?
Why do you sometimes need to round the percent?
Where do you see prices decrease by a percent in real life?
Would a $5 drop be a bigger percent decrease on a $10 item or a $50 item? Why?

Printable Lesson, Worksheet & Answer Key