Direct Variation Models

Examines how to solve word problems using direct variation models.

Grades 6 through 8 Material from CK-12

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Solve multi?step real? life and mathematical problems posed with positive and negative rational numbers in any form (whole numbers, fractions, and decimals), using tools strategically. Apply properties of operations to calculate with numbers in any form; convert between forms as appropriate; and assess the reasonableness of answers using mental computation and estimation strategies.


Use variables to represent quantities in a real? world or mathematical problem, and construct simple equations and inequalities to solve problems by reasoning about the quantities.




Recognize and represent proportional relationships between quantities.


Recognize and represent proportional relationships between quantities.



Graph proportional relationships, interpreting the unit rate as the slope of the graph. Compare two different proportional relationships represented in different ways. For example, compare a distance?time graph to a distance?time equation to determine which of two moving objects has greater speed.


Construct a function to model a linear relationship between two quantities. Determine the rate of change and initial value of the function from a description of a relationship or from two (x, y) values, including reading these from a table or from a graph. Interpret the rate of change and initial value of a linear function in terms of the situation it models, and in terms of its graph or a table of values.