CCSS.Math.Content.7.RP.A.2c
The standard
Represent proportional relationships by equations.
Common Core State Standards for Mathematics
What this standard means
Students need to write an equation for a proportional relationship using the form y = kx, where k is the constant rate. They should connect the equation to a table, graph, or story, and know what each variable means in context.
Mastery looks like choosing the correct rate, writing a clear equation, and using it to find missing values. Students often mix up x and y, use addition instead of multiplication, or write an equation from two numbers without checking for a constant ratio.
Ways to teach it
- Hands-on activity: Give pairs price tags and item cards, then have them build tables and write equations for total cost.
- Discussion prompt: Ask, “In the equation d = 55h, what does each letter and number mean in a road trip?”
- Quick assessment: Show a table with proportional values and ask students to write the equation and identify the constant rate.
- Real-world connection: Use a phone plan charging a fixed cost per gigabyte, and have students write an equation for total cost.
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Related standards
- CCSS.Math.Content.7.RP.A.2
Recognize and represent proportional relationships between quantities.
- CCSS.Math.Content.8.EE.B.5
Graph proportional relationships, interpreting the unit rate as the slope of the graph. Compare two different proportional relationships represented in differen...
- CCSS.Math.Content.7.RP.A.2a
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 observ...
- CCSS.Math.Content.7.RP.A.3
Use proportional relationships to solve multistep ratio and percent problems.