Multiple choice

Water is added to a 45 L mixture in a container that contains 40% of alcohol and the rest water, decreasing the percentage of alcohol to 25%. What amount of water is added?

  1. 18 L

  2. 33.75 L

  3. 27 L

  4. 145 L

  5. 165 L
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Initial alcohol = 40% of 45 = 18 L. Let x be the water added. New volume = 45 + x. New alcohol percentage = 18 / (45 + x) = 0.25. So, 18 = 0.25(45 + x), 72 = 45 + x, x = 27 L.

AI explanation

Using the method of alligation, compare the concentration of alcohol in the initial mixture (40%) with the concentration in the added water (0%) against the target concentration of 25%. The ratio of the initial mixture to the added water is calculated as (25 - 0) to (40 - 25), which equals 25 to 15, or 5 to 3. Since the 5 parts represent the initial 45 L, 1 part equals 9 L; the 3 parts of water added equal 27 L.

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