Multiple choice

A cleaning solution contains 30% vinegar and rest water. If 20% of the solution is substituted with water and this procedure is repeated two more times, what will be the approximate vinegar concentration in the final cleaning solution?

  1. 5%

  2. 12%

  3. 15%

  4. 18%

  5. 21%
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The vinegar concentration starts at 30%. Each substitution of 20% of the solution with water reduces the vinegar content by 20% (multiplying by 0.8). After three cycles, the concentration is 30% * (0.8)^3 = 30% * 0.512 = 15.36%, which is approximately 15%.

AI explanation

Using the replacement formula, the final concentration is the initial concentration multiplied by (1 minus the replacement fraction) raised to the power of the number of times the procedure is done. Here, the calculation is 30% multiplied by 0.8 cubed, which equals 15.36%. Therefore, the approximate vinegar concentration in the final solution is 15%.

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