Question

1 L of a 78% acid solution was mixed with 6 L of a 64% acid solution. Find the concentration of the new mixture.

Answer 1

The first solution contributes 0.78*1 = 0.78 L of acid.

The second contributes 0.64*6 = 3.84 L of acid.

There will be 7 L total of the new solution, and 3.84 + 0.78 = 4.62 total L of acid in it. So the new solution has a concentration of 4.62/7 = 0.66, or about 66%.