1. Constant of Proportionality
Pre-Algebra
Constant of Proportionality

2. Learning Target
I will be able to represent proportional relationships by equations.

3. 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.

4. 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.

5. 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

6. 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

7. 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