A chemist mixes a 40% acid solution and a 30% acid solution. How many liters of the 40% solution must be added to produce 50 liters of a solution that is 36% acid?

Explanation

To solve this problem, we need to determine the amount of the 40% acid solution (x) to mix with the 30% acid solution to achieve a 36% concentration in 50 liters. Let x be the liters of the 40% solution, implying 50 - x liters of the 30% solution.The equation for acid content is: 0.4x + 0.3(50 - x) = 18, where 18 represents 36% of 50 liters.Solving, we get: 0.4x + 15 - 0.3x = 18, which simplifies to 0.1x = 3, leading to x = 30.Therefore, combining 30 liters of the 40% solution with 20 liters of the 30% solution yields the desired 36% concentration in 50 liters. Options A, B, and D do not meet the acid concentration requirement, making Option C the correct choice.