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- What is a proportional relationship?
- How can I tell if the relationship is proportional?

A **proportional relationship** is when the growth pattern is multiplied by a **scale factor**.

**Situation**

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.

**Table***Malia's Birdseed *

Lbs | 1 | 2 | 3 | 4 |

Cost ($) | 3 | 6 | 9 | 12 |

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 .

**Graph**

You can tell if a graph is proportional because it is 1) linear (a line) and 2) goes through the origin (0, 0).

**Equation**The relationship between the quantities can be written in the form of y =

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