Florida B.E.S.T. MA.8.AR.3.1

Math8th GradeExtend understanding of proportional relationships to two-variable linear equations.

The Standard

Determine if a linear relationship is also a proportional relationship.

Florida B.E.S.T. Standards for Mathematics

Teacher's field guide

What This Standard Means

What Students Need to Do

Students use tables, graphs, equations, and contexts to check whether y/x stays constant. They connect a constant ratio with an equation y = kx and a graph through (0, 0).

What Mastery Looks Like

Given any representation, a student checks for a zero starting value and supports the answer with a ratio, equation, or graph. The student explains that y = mx + b is proportional only when b = 0.

Common Misconceptions

Students may call every straight-line graph proportional. They may focus only on constant slope and ignore a nonzero starting value, or calculate x/y instead of y/x.

How to Assess It

Exit ticket: Decide whether the table (x: 0, 2, 4; y: 3, 7, 11) is proportional. Justify your answer using the starting value, an equation, or ratios.

Lesson moves

Ways to Teach It

  1. Use cups and counters to model y = 2x and y = 2x + 3, then record both in tables and graphs.

  2. Students write a response to the prompt, “Explain why y = 4x + 5 is linear but not proportional.”

  3. Run a card sort with tables, graphs, equations, and situations; pairs match representations and label each set proportional or nonproportional.

  4. Compare a taxi fare with a starting fee to fruit sold at a fixed price per pound, then decide which relationship is proportional.

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Printable MA.8.AR.3.1 Worksheet

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