Multiple choice general knowledge math & puzzles

To 15 lts of water containing 20% alcohol, we add 5 lts of pure water. What is % alcohol?

  1. 20%

  2. 34%

  3. 15%

  4. 13%
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Initial alcohol content: 15 L x 20% = 3 L pure alcohol. When 5 L pure water is added, total volume becomes 20 L, but alcohol quantity remains unchanged at 3 L. New percentage = (3 L alcohol / 20 L total) x 100 = 15%. The key insight is that adding water dilutes the concentration without changing the amount of alcohol.

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