Another 10 kg of 68% acid solution was added to 5 kg of a 15% solution. Find the percentage of acid in the final solution.

Let’s determine the amount of acid in the first solution. To do this, let’s make a proportion.

5 kilograms – 100%,

x kilogram – 15%.

x = 5 * 15: 100 = 0.75 kilograms.

Determine the amount of acid in the second solution:

10 kilograms – 100%,

x kilogram – 68%.

x = 10 * 68: 100 = 6.8 kilograms.

6.8 + 0.75 = 7.55 kilograms.

The new solution weighed:

10 + 5 = 15 kilograms.

15 kilograms – 100%,

7.55 – x%.

x = 7.55 * 100: 15 = 50.3.

In the new solution, the acid concentration is 50.3%.

Answer: in the new solution, the acid concentration is 50.3%.