Since the tank is filled up to 3/4 of its maximum volume and this represents 14.4 liters of water, we have the following equation:
[tex]\frac{3}{4}\cdot V=14.4[/tex]where V represents the total volume of the tank. Since we have the measure of the width and the length in cm, we can convert 14.4 in cm^3 to get the following:
[tex]14.4l=14400cm^3[/tex]Now, we know that the formula for the volume of a rectangular prism is:
[tex]V=w\cdot l\cdot h[/tex]where w,l and h represent the width length and height respectively. Substituting the values that we have,we get the following equation:
[tex]\begin{gathered} \frac{3}{4}V=14400 \\ \Rightarrow0.75w\cdot l\cdot h=14400 \\ \Rightarrow0.75(40)(20)h=14400 \\ \Rightarrow600h=14400 \\ \Rightarrow h=\frac{14400}{600}=24 \\ h=24\operatorname{cm} \end{gathered}[/tex]therefore, the height of the tank is 24 cm