## 193. Math Puzzle $6 / 81$

Susanne and Michael had collected so many mushrooms that they could hardly carry them. The mushrooms consist of 85 percent water. After the mushrooms were dried, their mass was $15 \mathrm{~kg}$ less than before. Now they only contained 40 percent water. How many kilograms of fresh mushrooms had the children collected?
First, the amount of water in kilograms contained in the collected mushrooms must be calculated. Here, 85 percent is set to $x \mathrm{~kg}$ and 40 percent to $(x-15)$ kg. It follows that:

$$
x=\frac{85(x-15)}{40}, \quad 40 x=85 x-1275, \quad x=28.33
$$

85 percent water content means that $28.33 \mathrm{~kg}$ of water is contained in the collected mushrooms. Using this information, the total mass of the mushrooms can be calculated, as the $28.33 \mathrm{~kg}$ corresponds to 85 percent of the total mass $m$.

$$
m=\frac{28.33 \mathrm{~kg} \cdot 100}{85}=33.33 \mathrm{~kg}
$$

Susanne and Michael had collected and dried $33.33 \mathrm{~kg}$ of mushrooms.