The graph below shows the water level of a tank that is emptying over time.

• write a function that shows the relationship between water level and time.

• what would the water level be after 12 min?

• how long would it take before the tank is empty?

From inspecting the graph, you can identify the y-intercept and the slope of the line shown.

The y-intercept is 200 gallons.
The slope is 

             75-200
    m = = -12.5 gallons/minute
               10 -  0

Thus, y = 200 gallons - [12.5 gallons/minute ]t

To answer the 2nd question, let t = 12 minutes and calculate y(12).

To determine how long it wld take to empty the tank, set the above formula equal to zero and solve the resulting equation for t.

B.the point lies directly on the regression