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# Modeling with tables, equations, and graphs

See how relationships between two variables like number of toppings and cost of pizza can be represented using a table, equation, or a graph.
Math is all about relationships. For example, how can we describe the relationship between a person's height and weight? Or how can we describe the relationship between how much money you make and how many hours you work?
The three main ways to represent a relationship in math are using a table, a graph, or an equation. In this article, we'll represent the same relationship with a table, graph, and equation to see how this works.
Example relationship: A pizza company sells a small pizza for $\mathrm{}6$ . Each topping costs $\mathrm{}2$.

## Representing with a table

We know that the cost of a pizza with $0$ toppings is $\mathrm{}6$, the cost of a pizza with $1$ topping is $\mathrm{}2$ more which is $\mathrm{}8$, and so on. Here's a table showing this:
Toppings on the pizza $\left(x\right)$Total cost $\left(y\right)$
$0$$\mathrm{}6$
$1$$\mathrm{}8$
$2$$\mathrm{}10$
$3$$\mathrm{}12$
$4$$\mathrm{}14$
Of course, this table just shows the total cost for a few of the possible number of toppings. For example, there's no reason we couldn't have $7$ toppings on the pizza. (Other than that it'd be gross!)
Let's see how this table makes sense for a small pizza with $4$ toppings.
Here's the cost of just the pizza:
$\mathrm{}6$
Here's the cost of the $4$ toppings:
$4$ toppings $\cdot$ $\mathrm{}2$ per topping $=$ $\mathrm{}8$
This leads to the total cost of
$\mathrm{}6+\mathrm{}8=\mathrm{}14$.
How much would a small pizza with $5$ toppings cost?
$\mathrm{}$

## Representing with an equation

Let's write an equation for the total cost $y$ of a pizza with $x$ toppings.
Here's the cost of just the pizza:
$\mathrm{}6$
Here's the cost of $x$ toppings:
$x$ toppings $\cdot$ $\mathrm{}2$ per topping $=$ $x\cdot 2=2x$
So here's the equation for the total cost $y$ of a small pizza:
$y=6+2x$
Let's see how this makes sense for a small pizza with $3$ toppings:
$x=3$ because there are $3$ toppings
The total cost is $6+2\left(3\right)=6+6=\mathrm{}12$
Use the equation to find the cost of a small pizza with $100$ toppings.
$\mathrm{}$

## Representing with a graph

We can create ordered pairs from the $x$ and $y$ values:
Toppings on the pizza $\left(x\right)$Total cost $\left(y\right)$Ordered pair $\left(x,y\right)$
$0$$\mathrm{}6$$\left(0,6\right)$
$1$$\mathrm{}8$$\left(1,8\right)$
$2$$\mathrm{}10$$\left(2,10\right)$
$3$$\mathrm{}12$$\left(3,12\right)$
$4$$\mathrm{}14$$\left(4,14\right)$
We can use these ordered pairs to create a graph:

Cool! Notice how the graph helps us easily see that the total cost of the small pizza increases as we add more toppings.

## We did it!

We represented the situation where a pizza company sells a small pizza for $\mathrm{}6$, and each topping costs $\mathrm{}2$ using a table, an equation, and a graph.
What's really cool is we used these three methods to represent the same relationship. The table allowed us to see exactly how much a pizza with different number of toppings costs, the equation gave us a way to find the cost of a pizza with any number of toppings, and the graph helped us visually see the relationship.
Now let's give you a chance to create a table, an equation, and a graph to represent a relationship.

## Give it a try!

An ice cream shop sells $2$ scoops of ice cream for $\mathrm{}3$. Each additional scoop costs $\mathrm{}1$.
Complete the table to represent the relationship.
Scoops of ice cream $\left(x\right)$Total cost $\left(y\right)$
$2$$\mathrm{}3$
$3$$$4$$
$5$$$6$$

Write an equation to represent the relationship.
Remember to use $x$ for scoops of ice cream and $y$ for total cost.

Plot the points from the table on the graph to represent the relationship.
Be sure to plot the exact points in the table above!

## Comparing the three different ways

We learned that the three main ways to represent a relationship is with a table, an equation, or a graph.
What do you think are the advantages and disadvantages of each representation?
For example, why might someone use a graph instead of a table? Why might someone use an equation instead of a graph?
Feel free to discuss in the comments below!

## Want to join the conversation?

• Hello! I hope you are having a great day. I think that the advantages are that they can show a lot of information that is easily understood. Even the Table in functions can be easy to use and practical and you will find a lot of solutions for just one equation. Equations are also easier to find with small numbers and they also show the relationship between the x-axis and the y-axis. The disadvantages of Equations are that with big numbers, the answer will be weird. A Disadvantage of using the Table is that when you use decimals, the Table won't work. The Disadvantage of using a graph is that you can probably have two unpredictable variables. For me, I prefer using the table more than the graph and the equation. I think it is easier for me because I can double-check my answer with each number in the table. Thanks!
• I would argue that a 7-topping pizza is, indeed, not "gross". For example, the Costco Food Court combination pizza (which was discontinued in 2020) had six toppings on top of cheese. It was considered 'good pizza', based on all the positive reviews it received, as well as the despair people shared when Costco stopped selling it.
Another example is the supreme pizza at Papa Johns. This pizza also contains 6 toppings, and yet people still buy and enjoy it. Not to mention other chains, such as Pizza Hut, allow you to put up to 7 toppings on your pizza.
It really comes down to personal preference, but needless to say, I personally think that just because your pizza has 7+ toppings, doesn't mean that it's "gross".
• Meat lovers is also a great example to this, depending what types of meat and how many options are available!
• Did anyone else get the equation one wrong the first time then look at the answer and felt stupid?
• Yes, unfortunately.😢 Have you ever done one of those 30 question Unit Tests and get them all right until the last problem? yeets computer
• For any people having trouble with the ice cream scoop equation, I have a simple explanation.

Because the base cost of a cone with no scoops is one dollar, (0,1) The equation has a plus-one.( y = x + 1 )

It's just like the base pizza price equation which is 6\$ for a pizza with no toppings, (0,6) And each topping costs two dollars. so you are multiplying the amount of toppings by 2, and then you add the base price which is six. Therefore, the equation is, ( y = 2x + 6 )
• What would you guys put on a 100 topping pizza?
• What psychopath a 100 topping pizza, though?
• LoL! I don't even know! I don't even put one topping on my Pizza!