How many grams of a 15% salt solution should be added to 50 g of a 60% salt solution to get a 40% salt solution?

Let’s designate the mass of a 15% salt solution, which must be added to 50 g of a 60% salt solution to obtain a 40% salt solution in x.

Then the amount of salt that will be contained in a 15% salt solution is 0.15x.

Let’s calculate the amount of salt contained in 50 g of 60% salt solution:

50 * 0.6 = 30 (g).

After mixing 15% and 60% salt solutions, a 40% salt solution should be obtained, that is, the ratio of the mass of the salt contained in it to the total mass of the solution should be equal to 0.4:

(0.15x + 30) / (x + 50) = 0.4;

Since the problem deals with mass, x must be a positive number. Multiply both sides of the equation by x + 50:

0.15x + 30 = 0.4 (x + 50);

0.15x + 30 = 0.4x + 20;

0.25x = 10;

x = 40.

Answer: 40 g of a 15% salt solution.