CCSS.Math.Content.HSN-Q.A.2
The standard
Define appropriate quantities for the purpose of descriptive modeling.
Common Core State Standards for Mathematics · Quantities
What this standard means
Students need to choose what to measure or count before building a model. They should name the variables, units, and time frame, and decide which quantities matter for the question. They also need to leave out quantities that do not help answer it.
Mastery looks like a student explaining, “I will use miles driven, gallons used, and cost per gallon to compare trips.” Students often get stuck picking too many variables, using vague labels like “time,” or forgetting units. They may also choose numbers because they are available, not because they match the question.
Ways to teach it
- Give pairs a school lunch waste scenario and have them list measurable quantities, units, and one quantity they would ignore.
- Ask students to write: What quantities would you track to decide if our school needs a later start time?
- Show a short word problem and have students circle useful quantities, cross out distractors, and add missing units.
- Use a phone data plan comparison and ask students to define the quantities needed to decide the better deal.
Plan a lesson for CCSS.Math.Content.HSN-Q.A.2
Generate a complete lesson plan aligned to this standard, with objectives, activities, and materials. Free, no account needed.
Related standards
- CCSS.Math.Content.HSG-MG.A.2
Apply concepts of density based on area and volume in modeling situations (e.g., persons per square mile, BTUs per cubic foot).
- CCSS.Math.Content.HSN-Q.A.3
Choose a level of accuracy appropriate to limitations on measurement when reporting quantities.
- CCSS.Math.Content.HSG-MG.A.1
Use geometric shapes, their measures, and their properties to describe objects (e.g., modeling a tree trunk or a human torso as a cylinder).
- CCSS.Math.Content.8.F.B
Use functions to model relationships between quantities.