Graph relationships from tables

Detailed Explanation: Graph relationships from tables

Each row of a table can be turned into an ordered pair:

• The input is the quantity you choose or count. It goes on the horizontal $x$-axis.
• The output is the quantity that changes because of the input. It goes on the vertical $y$-axis.
• To graph an ordered pair $(x,y)$, move $x$ units right and $y$ units up from the origin.

Example

A movie ticket costs 8$. The table shows the total cost for different numbers of tickets.

Step 1: Identify the input and output.

The number of tickets is the input, because we choose how many tickets to buy.

The total cost is the output, because it depends on the number of tickets.

Label the axes:

• Horizontal axis: number of tickets
• Vertical axis: total cost in dollars

Step 2: Turn each row into an ordered pair.

Read each row as $(\text{number of tickets},\text{total cost})$:

Step 3: Plot the ordered pairs.

On the coordinate plane, plot:

• $(0,0)$: 0 tickets and 0$
• $(1,8)$: 1 ticket and 8$
• $(2,16)$: 2 tickets and 16$
• $(3,24)$: 3 tickets and 24$
• $(4,32)$: 4 tickets and 32$

Be sure to use a scale that reaches at least $4$ on the horizontal axis and 32$ on the vertical axis.

Step 4: Describe the pattern.

As the number of tickets increases by $1$, the total cost increases by 8$. The points show an increasing relationship.

These are discrete data points because you can buy whole tickets, not $2.5$ tickets. Therefore, leave the points unconnected. A line would suggest that every value between the points is possible.