Digits, Grade 8, Volume 1, Homework Helper

Key Concept

Proportional Relationships

Proportional relationships can be shown using tables, graphs, and equations. Each model below shows a proportional relationship where y is twice x.

Table A table shows a proportional relationship when one quantity is a constant multiple of the other quantity.

Table with callout.

Graph A graph shows points with a proportional relationship if a line that passes through the origin can be drawn through the points. For each point, the y-coordinate is a constant multiple of the x-coordinate.

A graph.

Equation Equations in the form y = mx represent proportional relationships. In the equation, m is the constant of proportionality, or the constant multiple y over x . Sometimes a k is used to represent the constant of proportionality. So an equation in the form y = kx is the same as an equation in the form y = mx.

2x: The constant of proportionality is 2.

The equation of the line is y = 2x.


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Table of Contents

Digits, Grade 8, Volume 1, Homework Helper Unit A: Number and Operations Unit B: Proportionality Unit C: Expressions, Equations, and Relationships English/Spanish Glossary Formulas Math Symbols Formulas Measures Properties