CCSS.Math.Content.HSA-CED.A
The standard
Create equations that describe numbers or relationships
Common Core State Standards for Mathematics · High School — Algebra
What this standard means
Students need to turn situations, patterns, and constraints into equations or inequalities. They should choose variables, define what the variables mean, and write expressions that match the relationship in the problem. They also need to handle linear, quadratic, exponential, and simple system situations when the context calls for them.
Mastery looks like a student explaining why an equation fits the situation, not just getting a formula on paper. Common sticking points are vague variable definitions, mixing up quantities and rates, ignoring units, and writing equations that fit one value but not the whole relationship.
Ways to teach it
- Hands-on activity: Give pairs cups, tiles, or paper clips, then have them build patterns, count totals, and write equations for step n.
- Discussion prompt: Ask, “What does each variable stand for, and how do you know the operation matches the story?”
- Quick assessment: Show a short word problem and three equations, then have students choose the best match and fix one wrong equation.
- Real-world connection: Use a phone plan, rideshare fare, or savings goal, and have students write an equation with clearly defined variables.
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Related standards
- CCSS.Math.Content.HSF-BF.A.1
Write a function that describes a relationship between two quantities
- CCSS.Math.Content.6.EE.A.2a
Write expressions that record operations with numbers and with letters standing for numbers.
- CCSS.Math.Content.HSA-CED.A.2
Create equations in two or more variables to represent relationships between quantities; graph equations on coordinate axes with labels and scales.
- CCSS.Math.Content.8.F.B
Use functions to model relationships between quantities.