You have 5 liters of Solution A, which is 50% diluted, and 15 liters of Solution B, which is 20% diluted. How much of Solution B must be added to Solution A to make Solution A 55% diluted?

A. 105 liters
B. −105 liters
C. The answer is extraneous.
D. 0.71 liters

1 answer

To determine how much of Solution B must be added to Solution A to achieve the desired concentration of 55%, we can set up an equation based on the amounts and concentrations of the solutions.

  1. Calculate the amount of solute in Solution A and Solution B.

    • For Solution A (5 liters at 50%): \[ \text{Amount of solute in Solution A} = 5 \text{ liters} \times 0.50 = 2.5 \text{ liters} \]

    • For Solution B (15 liters at 20%): \[ \text{Amount of solute in Solution B} = 15 \text{ liters} \times 0.20 = 3.0 \text{ liters} \]

  2. Let \( x \) be the amount of Solution B (in liters) to be added to Solution A. When we add \( x \) liters of Solution B to Solution A, the total volume becomes: \[ 5 + x \text{ liters} \] The total amount of solute now will be: \[ 2.5 \text{ liters (from Solution A)} + 0.2x \text{ liters (from Solution B)} \] Here, \( 0.2x \) comes from the concentration of Solution B (20%).

  3. We want the new solution to be 55% diluted. Therefore, we set up the equation: \[ \frac{2.5 + 0.2x}{5 + x} = 0.55 \]

  4. Now we can solve this equation: \[ 2.5 + 0.2x = 0.55(5 + x) \] Expanding the right side: \[ 2.5 + 0.2x = 2.75 + 0.55x \]

  5. Rearranging gives: \[ 2.5 - 2.75 = 0.55x - 0.2x \] \[ -0.25 = 0.35x \] \[ x = \frac{-0.25}{0.35} = -\frac{25}{35} = -\frac{5}{7} \approx -0.714 \text{ liters} \]

Since we obtained a negative value for \( x \), it indicates that you cannot achieve a 55% concentration by adding any amount of Solution B; instead, you would need to remove some volume of Solution B.

Hence, this leads us to conclude that the answer is:

C. The answer is extraneous.