1. Rate of Change
A ratio (fraction) of the amount of change in the dependent variable (output) to the amount of change in the independent variable (input)
Rate change in output (y)
Of = change in input (x)
Change

2. Example 1 page 77 Day 1 Day 2 Day 3 Day 4 1 3 6 8 15 45 90 120
Number of lawns 1 3 6 8
Amount earned 15 45 90
120
Independent variable (x) → number of lawns Dependent variable (y) → amount earned
Change in $ 45 – 15 = – 45 = – 90 = all equal to
Change in lawns 3 – 1 = – 3 = – = $15 per lawn
These Rates of Change are constant since they are all the same. If Rates of Change are not the same, they are said to be variable

3. Your Turn page 77
Answer the “Your Turn” question with a partner

4. Using graphs to find Rate of Change
Explore activity page 78
Do steps A thru D and answer Reflect questions 2 & 3

5. Calculating Slope (m) page 79
When the rate of change of a relationship is constant, any segment of its graph has the same steepness. This constant rate of change is called the slope of the line
The slope of a line is the ratio (fraction) of the change in y-values over the change in x-values slope (m) = y2 – y1
x2 – x1
you can also find slope by using two points on a graph and finding the rise over the run between the two points
slope (m) = vertical change (rise)
horizontal change (run)

6. Your Turn page 79
Do “Your Turn” on page 79 with a partner

7. Assignment
#1 – 8 page 80
#10 – 18 evens pages 81 & 82