Percent and Scaling

Lesson 7

Math

Unit 5

7th Grade

Lesson 7 of 19

Objective


Find the percent of increase or decrease given the original and new amounts.

Common Core Standards


Core Standards

  • 7.RP.A.3 — Use proportional relationships to solve multistep ratio and percent problems. Examples: simple interest, tax, markups and markdowns, gratuities and commissions, fees, percent increase and decrease, percent error.

Foundational Standards

  • 6.RP.A.3.C

Criteria for Success


  1. Determine the amount of increase of decrease in a situation.
  2. Identify the starting or original value.
  3. Find the percent increase or decrease by dividing the amount of change by the starting value. 

Tips for Teachers


  • Lessons 5–8 address percent increase and decrease problems. In this lesson, students find the percent that represents the amount of increase or decrease in a situation. 
  • Students continue to reason abstractly, making meaning of the quantities in the problems to understand their relationships before doing any calculations (MP.2). 
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Anchor Problems


Problem 1

At the end of Quarter 1, Winston’s math grade was a 72. He made a goal to improve his grade for Quarter 2 by correcting any mistakes he made on his homework assignments. At the end of Quarter 2, Winston’s grade increased to an 80. 

By what percent did Winston’s grade improve? 

Guiding Questions

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Problem 2

In the Mattapan Chess Club, each player has a specific level, either Beginner or Intermediate, that is used to pair players in competition. Last year, there were 24 players at the Intermediate level and 20 players at the Beginner level. This year the number of Intermediate players increased by 25%, and the number of Beginner players decreased by 10%. 

Was there an increase or decrease in overall membership? Find the overall percent change in membership of the club.

Guiding Questions

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References

Illustrative Mathematics Chess Club

Chess Club, accessed on Dec. 18, 2017, 9:02 p.m., is licensed by Illustrative Mathematics under either the CC BY 4.0 or CC BY-NC-SA 4.0. For further information, contact Illustrative Mathematics.

Modified by Fishtank Learning, Inc.

Problem Set

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Target Task


In April, Justin sent 675 text messages on his phone. In May, he sent 621 text messages. 

By what percent did the number of text messages Justin sent decrease from April to May? 

Student Response

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Additional Practice


The following resources include problems and activities aligned to the objective of the lesson that can be used for additional practice or to create your own problem set.

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Lesson 6

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Lesson 8

Lesson Map

A7CB09C2-D12F-4F55-80DB-37298FF0A765

Topic A: Percent, Part, and Whole

Topic B: Percent Increase and Decrease

Topic C: Percent Applications

Topic D: Scale Drawings

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