Interpreting Slope of a Line

Slope is the number of units a non-vertical line rises (or falls) for each unit of horizontal change.

Slope can often be applied to real-life problems to compare change over time. This application is called rate of change and can be thought of as slope with units. When analyzing rate of change, results are reported using units such as “feet per second” or “dollars per day”.

Olympic Hurdles

y= -0.018x + 47.754

The slope is…. What is the meaning of it?

The y-intercept is… What is the meaning of it?

Interpretation

• Slope - For each year of the Olympics since 1970, the time for the hurdles is expected to decrease 0.018 (18-thousandths) of a second.

• Y-Intercept - At year zero (which is 1970), the time was 47.754 seconds.

y= -0.018x + 47.754

DeforestationYear since 1997

Deforestation per sq. mile

1 5,034

2 6,501

3 6,663

4 7,658

5 7,027

6 9,845

7 9,500

8 10,088

y= 705.81x + 4613.4

The slope is…. What is the meaning of it?

The y-intercept is… What is the meaning of it?

Interpretation

• Slope - For each year since 1997, the deforestation is expected to increase at a rate of 705.81 square miles per year.

• Y-intercept - In year zero (which is 1997), 4613.4 square miles were deforested.

y= 705.81x + 4613.4