How much do you need to mix a 10% and 30% acid solution to get 8 kg of a 15% solution.

Let us express the required mass of a 10% solution, for which we use the variable a.

Therefore, the required mass of the second solution can be expressed in the form (8 – a).

Since we know that the solution obtained by mixing is 15%, then we write down the equation and find out how much it will be necessary to mix the first and second solutions:

(0.1a + 0.3 * (8 – a)): 8 = 0.15;

0.1 a + 2.4 – 0.3 a = 1.2;

-0.2a = -1.2;

a = 6;

8 – 6 = 2.

Answer: It will be necessary to use 6 kg of a 10% solution and 2 kg of a 30% solution.