GreenlightTestPrep wrote:
How many liters of 20% vinegar solution should be added to 4 liters of 50% vinegar solution to make a 30% vinegar solution?
When solving mixture questions, it can be useful to sketch the solutions with the ingredients SEPARATED. 50% of 4 liters = 2 liters. So, the original mixture contains
2 liters of vinegar
Let x = the volume (in liters) of 20% solution required
So, this solution contains
0.2x liters of vinegar
We get:
We want the resulting solution to be 30% vinegar .
In other words, we want: \(\frac{2 + 0.2x}{4+x}=\frac{3}{10}\) (aka 30%)
Cross multiply: \((10)(2 + 0.2x) = 3(4+x)\)
Expand: \(20 + 2x = 12+3x\)
Solve: \(x = 8\)
Answer: 8
Cheers,
Brent