# If I Could Buy Anything- Math is Everywhere

- Author:
- jaronovitz, GeoGebra Materials Team

- Topic:
- Mathematics

## Unit Price and Constant of Proportionality

Explore how unit price and constant of proportionality are related and how they can be represented using a table, a graph, an equation, and a verbal description.
Think of something that you enjoy and would like to buy the next time you go to the store. For purposes of this activity, keep the price under $10. Use the purple slider to set your unit price.

## Use the slider scale to set the unit price. Round to the nearest whole dollar.

## Representing a Proportional Relationship Using a Table

Describe the table- do you notice a pattern? How does buying 1 more unit (x) impact the cost?

## Finding the Constant of Proportionality from a Table

Divide each cost (y) by the quantity (it's related x). What do you notice?

## Is there a point on the graph that when extended the line would always cross?

## Representing a Proportional Relationship Using a Graph

Desctibe the shape of the graph.

## The Origin

What is the cost when the quantity is zero?

## Explain the Relationship.

In you own words how you would use the number of items you buy and the unit price to find the cost.

## Finding the Unit Price from a Graph of a Proportional Relationship

How can you find the unit price (*k=constant of proportionality*) from the graph? Select all that apply.

## Using Your Unit Price to Write the Rule. y=kx

Write an equation using your unit price to show the relationship between the quantity and cost.

## Use what you know to make a prediction.

What would your total cost be if you were buying 20 items?

## What's Your Word Problem?

Write your own word problem using the item you selected and it's unit price.