[tex]\begin{gathered} \text{First Pump}=\frac{1\text{ tank}}{3\text{ hour}}\text{ or a rate of 1/3 tank/h} \\ \text{Second Pump}=\frac{1\text{ tank}}{2\text{ hour}}\text{ or a rate of 1/2 tank/h} \\ \text{If both pumps are working, then add the two rates} \\ \frac{1}{3}\text{tank/h}+\frac{1}{2}\text{tank/h}=\frac{5}{6}\text{tank/h} \\ \text{The new rate is }\frac{5}{6}\text{tank/h, but since we only one to know the rate of one tank,} \\ \text{we divide both numerator and denominator by }5 \\ \frac{\frac{5}{5}}{\frac{6}{5}}\text{tank/h} \\ \rightarrow\frac{1}{1.2}\text{tank/h} \\ \text{Which means, that when both pumps are working, it would only take 1.2 hours or} \\ \text{1 hour and 12 minutes} \end{gathered}[/tex]
