Multiple choice

Directions: Select the correct alternative from the given choices. A mixture of alcohol and water comprises 80% alcohol. First, 20% of the mixture is replaced with• water and then the volume of the resultant mixture is increased• by 20% by adding only alcohol. If the entire process is then repeated once all over again, what is percentage of alcohol in the final mixture?

  1. 63.33%

  2. 72.28%

  3. 61.25%

  4. 81.24%
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Initial: 80% alcohol. Replace 20% with water: 80% of 0.8 = 64% alcohol. Increase volume by 20% with alcohol: (0.64 + 0.2) / 1.2 = 0.84 / 1.2 = 70%. Repeat: 70% of 0.8 = 56%. Increase by 20% with alcohol: (0.56 + 0.2) / 1.2 = 0.76 / 1.2 = 63.33%.

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