Question

A gallon if water is added to 6 quarts of a solution that is 50% acid. What percent of the new solution is acid?

Answer 1

The old solution contains 6(0.5) = 3 quarts of acid.
The gallon of water has no acid.
Total amount of acid in new solution = 3 quarts.

The old solution has volume 6 quarts.
The gallon of water has volume 4 quarts.
Total volume of new solution = 4 + 6 = 10 quarts.

The new solution is 3/10 = 0.3 = 30% acid.