Tank filling

The tank is filled in 1 hour and 12 minutes with a pump with a capacity of 25 l/s. How long does filling the tank with a 20 l / s pump take?

Result

t₂ = 1:30 h

Step-by-step explanation:

$$\begin{gathered} t_1=1+12/60=\frac{6}{5}=1.2\text{h} \\ {Q}_1=25\text{l/s} \\ {Q}_2=20\text{l/s} \\ {t}_2:t_1=Q_1:Q_2 \\ {t}_2=t_1\cdot \frac{Q_1}{Q_2}=\frac{6}{5}\cdot \frac{25}{20}=\frac{6\cdot 25}{5\cdot 20}=\frac{150}{100}=1.5=1:30\text{h} \end{gathered}$$

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