Multiple choice

Directions : Select the correct alternative from the given choices. There is a 40 litre solution of milk and water with concentration of milk as 30%. Initially, 10 litres of the solution is replaced with 10 litres of water. After some time, 10 litres of the new solution is replaced with 10 litres of milk. What is the concentration of milk in the solution now?

  1. 58.125%

  2. 41.875%

  3. 35.625%

  4. 64.375%
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Initial: 40L, 30% milk = 12L milk, 28L water. Replace 10L solution with 10L water: 10L of solution contains 3L milk, 7L water. Remaining: 9L milk, 21L water + 10L water = 9L milk, 31L water. Replace 10L of new solution (which is 9/40 milk = 22.5% milk) with 10L milk: 10L of new solution has 2.25L milk. Remaining milk = 9 - 2.25 = 6.75L. Add 10L milk: 6.75 + 10 = 16.75L milk. Concentration = 16.75 / 40 = 41.875%.

AI explanation

Initially, the 40 litre solution contains 12 litres of milk, and replacing 10 litres with water leaves 12 times 0.75, or 9 litres of milk. Then 10 litres of this new solution is replaced with milk, which adds 10 litres of milk while removing 2.25 litres of milk, resulting in a final milk volume of 16.75 litres. The final concentration of milk is 16.75 divided by 40, which equals 41.875 percent.

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