a solution contains 3% salt. How much water should be added to 60 ounces of this solution to make a 1.8% solution?
If a 60-ounce solution contains 3% salt, then the salt is \(\frac{3}{100} \cdot 60 = 1.8\) ounces. We want to figure out the weight of the solution that is going to make 1.8 ounces equal to 1.8% of its weight. Let x be the weight of that solution:
\(1.8 = \frac{1.8}{100} \cdot x\\ x = 100\)
That means \(100-60=\boxed{40}\) ounces of water should be added.