13.010. A pump can extract $2 / 3$ of the water from a pool in 7.5 min. After working for 0.15 h, the pump stopped. Find the capacity of the pool, if after the pump stopped, there was still 25 m $^{3}$ of water left in the pool.
Solution.

Let $x$ m $^{3}$ be the capacity of the pool. In 7.5 minutes, the pump can extract $\frac{2}{3} x$ water. In $0.15 \text{ h} = 9$ minutes, the pump extracted $\frac{9 \cdot \frac{2}{3} x}{7.5}=0.8 x$ water. In the pool, $0.2 x$ water remained. According to the problem, $0.2 x=25$, from which $x=125$.

Answer: $125 \text{ m}^{3}$.