Multiple choice

Several liters of acid were drawn off 54-liter vessel full of acid and an equal amount of water was added. Again, the same volume of the mixture was drawn off and replaced by water. As a result, the vessel contained 24 liters of pure acid. How much of the acid was drawn off initially?

  1. 12 lts

  2. 16lts

  3. 15lts

  4. 18lts

  5. 24lts

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let x be the amount drawn off. The concentration of acid after two replacements is 54 * (1 - x/54)^2 = 24. (1 - x/54)^2 = 24/54 = 4/9. 1 - x/54 = 2/3. x/54 = 1/3. x = 18.

AI explanation

Using the formula for replacement, the final amount of acid is Initial Amount * (1 - Replaced Volume / Total Volume)^n. We are given the initial amount as 54 liters, the final amount as 24 liters, and n = 2. Substituting the values gives 24 = 54 * (1 - x / 54)^2. Dividing both sides by 54 yields 4/9 = (1 - x / 54)^2, so taking the square root gives 2/3 = 1 - x / 54. Solving for x gives x / 54 = 1/3, meaning x = 18. The amount of acid drawn off initially was 18 liters.