Final answer:
To make 500 L of a 15% acid solution, 375 L of a 10% acid solution should be mixed with 125 L of a 30% acid solution.
Step-by-step explanation:
To determine how much 10% acid solution must be mixed with a 30% acid solution to make 500 L of a 15% acid solution, you can use an equation based on total amounts of pure acid in the solution. Let's denote the volume of the 10% solution as x liters and the volume of the 30% solution as (500 - x) liters. The equation to represent the total acid after mixing will be:
0.10x + 0.30(500 - x) = 0.15 × 500
Now, solve for x:
0.10x + 150 - 0.30x = 75,
-0.20x = -75,
x = 375 L.
Therefore, 375 liters of the 10% acid solution should be mixed with 125 liters (500 L - 375 L) of the 30% acid solution to obtain 500 liters of a 15% acid solution.