80 g of pure water was added to a 30% salt solution, after which the concentration of the solution

80 g of pure water was added to a 30% salt solution, after which the concentration of the solution became 18%. Find the initial weight of the solution.

Let x be the mass of the solution at 30% salt. This means that the salt in such a solution will be 0.3x. If you add 80 g or x + 80 to this solution, then the salt in it will already be (x + 80) * 0.18. Since the mass of salt in both solutions is the same, both of these expressions can be equated:

0.3x = (x + 80) * 0.18.

Let’s solve this equation:

0.3x = 0.18x +14.4;

0.3x – 0.18x = 14.4;

0.12x = 14.4;

x = 120 g initial weight of the solution.

Answer: the initial weight of the solution is 120 g.