Since the volume of water depends on the floor area, the floor area is the independent variable while the minimum water volume is the dependent variable.
Let x represents the floor area
Let y represent the miminum volume of water
The rate of change is the ration of the change in y to the change in x
Let the rate of change be represented by dy/dx
[tex]\begin{gathered} \frac{dy}{dx}=\text{ }\frac{y_2-y_1}{x_2-x_1} \\ \end{gathered}[/tex]Considering the first two rows of the table, since the rate of change does not differ despite the rows picked
[tex]\begin{gathered} x_1=25,y_1=39,x_2=50,y_2=78 \\ \frac{dy}{dx}=\text{ }\frac{78-39}{50-25} \\ \frac{dy}{dx}=\frac{39}{25} \\ \frac{dy}{dx}=1.56 \end{gathered}[/tex]