A proportional relationship is when the growth pattern is multiplied by a scale factor.
We'll be exploring how a relationship can be expressed in a situation. For example, Malia buys bird 1 lb. of bird seed for $3. If she buys 2 lbs., she would spend $6. Since she is charged the same amount per pound, and there is no initial fee, this is a proportional relationship.
You can write each point as a fraction in simplest terms and if they are all equal, then it's a proportion. Ex. because they all simplify to .
You can tell if a graph is proportional because it is 1) linear (a line) and 2) goes through the origin (0, 0).
The relationship between the quantities can be written in the form of y = kx. k is the constant of proportionality. The constant of proportionality is the same as the scale factor.
For equations, the equation is in the form of y = kx. k is the constant of proportionality. The instructor mentioned that if it is a one-step equation it's proportional. NOTE: y = x + k, which is a one-step equation, is NOT proportional. Only one step equations in the form y = kx are proportional.
Source: Danielle Kunetz
Source: Ms. Newburn