Graph Ratio Tables

First let's talk about the coordinate plane. The coordinate plane is formed when two number lines intersect (cross) at the zero point. Where the two number lines cross is called the origin. The horizontal number line is called the X-Axis. There vertical number line is called the Y-Axis. The coordinate system look alike this:

Today we are only going to focus on what is called the first quadrant. The first quadrant looks like this.

Practice Sites

Shodor - Give the ordered pair for the house. Make sure to delete the question marks before typing your coordinates.

XP Math - Soccer - Plot the point correctly to score a goal.

Billy Bug - Move the bug to the correct point. How fast can you do 10?

In both of these examples each mark on the number line is plus one form the previous number. You can number the number lines any way you want. You can count by 2's, 5's, 100'2, whatever makes your graph easy to use. This example shows that even decimals can be used in the coordinate plane.

Let's talk about how to put a point on the graph. We already talked about the X-Axis (horizontal {side to side}) and there Y-Axis (vertical {up and down}). When we graph a point we use what is called an ordered pair. That is two points,one on the X-Axis called the X Coordinate, and one on the Y-Axis, called the Y Coordinate. The point where those two numbers meet is the point on the graph. An ordered pair always looks like this:

(X-Coordinate, Y-Coordinate).

For example (3, 4) means 3 one the X-Axis and 4 on the Y-Axis. Let's look at how to put this point on the graph. To place a point on the graph look at the X coordinate. Find the positive 3 on the X-Axis. Now look at the Y coordinate. Find the positive 4 on the Y-Axis. Follow the line up from the 3 on the X-Axis and follow the line to the right form the 4 on the Y-Axis. Where the two lines meet place a dot. That point is at (3,4). Look at the example below.

Now let's use the coordinate system to graph a ratio table.

First look at your ratio table. The first column will be the X coordinate so the title of this column will be the name of the X-Axis. The second column will be the Y coordinate so it will be the name of the Y-Axis. (If the table is a horizontal table the top line is the X-coordinate and the bottom row is the Y coordinate.) Look at our example table:

Now we create a graph. The X-Axis will be Number of Dollars and the Y-Axis will be Number of Quarters. We will number the X-Axis by 1's. Since the numbers for the Y-Axis get pretty big, let's not number the number lines by 1's. Instead let's number by 2's.