CCSS.Math.Content.7.RP.A.2b
The standard
Identify the constant of proportionality (unit rate) in tables, graphs, equations, diagrams, and verbal descriptions of proportional relationships.
Common Core State Standards for Mathematics
What this standard means
Students need to find the unit rate in different forms. In a table, they compare y to x. On a graph, they use a point like (1, r) or divide y by x. In an equation, they connect the number multiplying x to the rate. In words or diagrams, they identify “per 1.”
Mastery means students can move between forms and name the same rate each time, with units. Common trouble spots are mixing up x and y, using additive patterns instead of multiplication, choosing a nonzero point without dividing, and forgetting that the graph must go through the origin for proportional relationships.
Ways to teach it
- Have students build ratio tables with colored tiles, then label the unit rate for each table they create.
- Ask students: Which is the better buy, 12 ounces for $3 or 20 ounces for $6, and how do you know?
- Show a table, graph, equation, and sentence, then have students write the unit rate with units on a sticky note.
- Bring in grocery ads and have students calculate price per ounce, per item, or per pound for three products.
Plan a lesson for CCSS.Math.Content.7.RP.A.2b
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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.2c
Represent proportional relationships by equations.