Multiple choice

A mixture of 70 liters of alcohol and water contains 10 \% of water. How much water must be added to the above mixture to make the water 12.5 \% of the resulting mixture?

  1. 3.3 liters

  2. 3 liters

  3. 2.8 liters

  4. 2 liters

  5. 1.5 liters
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D Correct answer
Explanation

In 70 liters of mixture, water = 10% of 70 = 7 liters, alcohol = 63 liters. Let x liters of water be added. New mixture volume = 70 + x liters. Water content = 7 + x liters. Given: (7 + x)/(70 + x) = 12.5% = 0.125. Solving: 7 + x = 0.125(70 + x), 7 + x = 8.75 + 0.125x, 0.875x = 1.75, x = 2 liters.

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