Multiple choice

If 20 litres of solution containing 15% alcohol is mixed with 30 litres of solution containing 18% alcohol, find the concentration of alcohol in the resulting solution.

  1. 15 4 5 %

  2. 16 4 5 %

  3. 17 4 5 %

  4. 18 4 5 %

  5. 14 1 5 %
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B Correct answer
Explanation

The first solution contains 20 x 15/100 = 3 litres of alcohol, and the second contains 30 x 18/100 = 5.4 litres. The mixture therefore has 8.4 litres of alcohol in 50 litres, giving 8.4/50 x 100 = 16.8%, or 16 4/5%.

AI explanation

The first solution contributes 15 percent of 20 liters, which is 3 liters of alcohol. The second solution contributes 18 percent of 30 liters, which is 5.4 liters of alcohol, making the total alcohol 8.4 liters in a 50 liter mixture. Dividing 8.4 by 50 gives 0.168, which when multiplied by 100 results in a concentration of 16.8 percent, or 16 and 4 fifths percent.

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