# Constant of Proportionality - Kyrene School District Pre-Algebra Constant of Proportionality Learning Target I will be able to represent proportional relationships by equations. Constant of Proportionality The graph of a proportional relationship is a straight line that passes through the origin. Proportional quantities can be described by the equation y= kx, where k is a constant ratio. Constant of Proportionality Equation for constant of proportionality is y = kx We can tell that the relationship is directly proportional by looking at the graph. The graph is a straight line that passes through the origin.

Constant of Proportionality Equation for constant of proportionality is y = kx Create a table using the points from the graph: Total price (y) 20 40 60 80 100 Total pounds (x)

2 4 6 8 10 Divide total price by total pounds Constant of Proportionality Equation for constant of proportionality is y = kx Create a table using the points from the graph: Total price (y)

20 40 60 80 100 Total pounds (x) 2 4 6 8 10

Divide total price by total pounds 10 10 10 10 10 Constant of Proportionality Equation for constant of proportionality is y = kx Ratio is constant for all points on the graph 1:10 So the constant of proportionality (k) = 10.

Equation: y = 10x Create a table using the points from the graph: Total price (y) 20 40 60 80 100 Total pounds (x) 2 4 6

8 10 Divide total price by total pounds 10 10 10 10 10