Suppose a theme park charges a $10 entrance fee, and $6 for each ride.[br][br]We can construct a table of values to show how the total cost ($[i]y[/i]) is related to the number of rides [i]x[/i]:[br][br][table][tr][td]Number of rides ([i]x[/i])[/td][td]0[/td][td]1[/td][td]2[/td][td]3[/td][td]4[/td][/tr][tr][td]Total cost ($[i]y[/i])[/td][td]10[/td][td]16[/td][td]22[/td][td]28[/td][td]34[/td][/tr][tr][td][/td][td][color=#ff0000]+6[/color][math]\longrightarrow[/math][/td][td][color=#ff0000]+6[/color][math]\longrightarrow[/math][/td][td][color=#ff0000]+6[/color][math]\longrightarrow[/math][/td][td][color=#ff0000]+6[/color][math]\longrightarrow[/math][/td][td][/td][/tr][/table][br]In the next applet, plot the points (x,y) and observe the shape they make.[br][color=#0000ff][br]To plot them, write them as a pair (x,y) in the + entry bar and hit Enter.[/color]

When we plot these points (x,y) on a Cartesian plane, we see that they lie on a straight line. We say that the relationship between the variables is [b]linear[/b].