GMAT Focus EditionQuantitative ReasoningMedium
A chemist has two solutions. Solution A is 30% acid, and Solution B is 70% acid. How many liters of Solution A must be mixed with 6 liters of Solution B to obtain a solution that is 40% acid?
- A18 liters
- B6 liters
- C12 liters
- D9 liters
Show answer & explanationAnswer & explanation
Correct answer: A. 18 liters
Let 'x' be the amount of Solution A. The total amount of acid in the final mixture must equal the sum of acid from Solution A and Solution B. Set up the equation: 0.30x + 0.70(6) = 0.40(x + 6) and solve for x.
Why the other options are wrong
- B. This might result from a calculation error or incorrect setup of the equation.
- C. This is a common distractor if the proportions are misapplied.
- D. This could be a miscalculation after setting up the equation.
Mixture Problems (Algebraic)
Problems involving combining two or more solutions with different concentrations to achieve a desired final concentration, often solved using algebraic equations.
- Total amount of solute = Sum of solute from each component.
- Total volume of mixture = Sum of volumes of components.
- Concentration = (Amount of Solute / Total Volume) × 100%.
Memory trick: Balance the acid, balance the volumes, then solve!