Proportional Relationships

Objective

Compare proportional and non-proportional relationships.

Common Core Standards

Core Standards

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• 7.RP.A.2.A — Decide whether two quantities are in a proportional relationship, e.g., by testing for equivalent ratios in a table or graphing on a coordinate plane and observing whether the graph is a straight line through the origin.

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• 6.RP.A.3

Criteria for Success

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1. Identify and explain examples of non-proportional relationships.
2. Represent non-proportional relationships in tables and graphs and compare to features of proportional relationships.
3. Determine if a table or graph represents a proportional relationship.

Tips for Teachers

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This lesson is a good opportunity for students to construct arguments and defend their decisions around if a relationship is proportional or not. They may also work in pairs to listen to and critique the arguments of others (MP.3).

Fishtank Plus

• Problem Set
• Student Handout Editor
• Vocabulary Package

Anchor Problems

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Problem 1

Syrus is 12 years old and has a younger sister, Samira, who is 6 years old. Syrus says, “Our ages are in a proportional relationship because I am two times as old as my sister.”

Problem 2

At the zoo, you can buy tickets to take a train ride between exhibits. Each ticket costs $0.50; however, there is a deal that if you buy 10 tickets, you only pay$4.00.

Is the cost of the tickets proportional to the number of tickets you buy? Create a table with some values and plot the points on a coordinate plane.

Problem 3

Four tables and four graphs are shown below. Which tables and graphs represent proportional relationships? Explain your reasoning for each one.

Problem Set

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

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Two ice cream shops are located across the street from one another on a busy street.

• At Max’s Ice Cream shop, you can buy a sundae with unlimited toppings for $5 per sundae. • At Mary’s Ice Cream shop, you can buy a sundae by paying$3.50 for the ice cream and then \$0.75 for each topping.

At which ice cream shop is the cost of the sundaes (including the toppings), proportional to the number of sundaes purchased? Justify your answer with tables, graphs, or an explanation.

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