Lesson objective: Solve problems by interpreting information from a linear graph, specifically what the slope tells us about how the input and output values are changing together.
This lesson provides an opportunity for students to apply their knowledge and understanding of linear graphs and their slopes to a reallife situation. Students are asked to describe the status of three scuba divers using a depth vs. time graph for each one, and then read a depth vs. time and pressure vs. time graph side by side to determine how pressure changes during an ascent.
Key Concept students will use:

The slope of a line gives information about how the values of x and y change together (as the value of x increases the value of y either increases or decreases, and as the value of x decreases, the value of y either increases or decreases).
Skills students will use:
 calculating the slope of a linear graph
 interpreting the slope of a linear graph, including the slope of a horizontal line
 finding missing points on a given line
Students engage in Mathematical Practice 4 (Model with mathematics) as they anaylze relationships summarized in graphs, and make conclusions in the context of the situation the graphs represent.
Key vocabulary:
 decreasing
 increasing
 slope
Special materials needed: