Slope is a number assigned to a line that describes the steepness of the line. It is actually a ratio comparing the vertical change of the line to the horizontal change; hence, the moniker rise over run. The larger the absolute value of the slope the steeper the line will be. It makes sense that the flattest line, a horizontal line, has slope zero, and the steepest line, a vertical line, would have a slope represented by the largest number there is. Since there is no largest number, the slope of vertical lines is undefined.

From A Graph

To find the slope of a line given its graph one simply needs to find any two points on the line and count how far one goes up (or down) and left (or right) to get from one point to the other. Generally, we look for "corner" points to avoid having to guess at fractions.


Find the slope of the lines graphed below:


learning activity After deciding what the slope of each line is, put your mouse on the line to see if you are correct.