## Task 3 - 060833

Given are $3000 \mathrm{~g}$ of a 7.2 percent sodium chloride solution in water (i.e., in every $100 \mathrm{~g}$ of the solution, exactly 7.2 g of sodium chloride is contained). By boiling this solution, so much water evaporates that exactly $2400 \mathrm{~g}$ of the concentrated solution remains.

What is the percentage of the resulting solution?
In 100 g of the solution, there are exactly 7.2 g of table salt. Consequently, the amount of table salt in 3000 g of the solution is

$$
30 \cdot 7.2 \mathrm{~g}=216 \mathrm{~g}
$$

Since the amount of table salt remains constant during evaporation, there are also exactly 216 g of table salt in the new solution of 2400 g. Therefore, the new solution contains exactly $216 \mathrm{~g} : 24=9 \mathrm{~g}$ of table salt per 100 g, i.e., the solution is 9 percent.