25. Fresh mushrooms contain $90 \%$ water, and when they were dried, they became lighter by 15 kg with a moisture content of $60 \%$. How much did the fresh mushrooms weigh?
25. If there were $x$ kg of fresh mushrooms, then the dry mass in them is $0.1 x$ kg. After drying, the dry mass became $40\%$, and the water $-60\%$. This means that at a moisture content of $60\%$, the mushrooms became $\frac{0.1 x \cdot 100\%}{40\%}=\frac{1}{4} x$ (kg), and $ \frac{3}{4} x$ kg of water evaporated, which is 15 kg. Therefore, $\frac{3}{4} x=15$, from which $x=\frac{15 \cdot 4}{3}=20$ (kg).