Multiple choice

Rishav had a cylindrical container, which was full of whisky. Seven litres of whisky was removed and replaced by beer. Again, 7 litres of the mixture was removed and replaced by beer. The proportion of whisky left in the container then was 25/36 of the total mixture (in the container). What is the capacity of the container?

  1. 35 L

  2. 42 L

  3. 30 L

  4. 28 L

  5. 45 L
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let capacity be C. After 2 replacements, whisky remaining = C * (1 - 7/C)^2. Given this equals (25/36)C. So (1 - 7/C)^2 = 25/36. Taking square root, 1 - 7/C = 5/6. 7/C = 1/6, so C = 42.

AI explanation

Using the replacement formula, the final proportion of whisky is (V minus 7) divided by V, raised to the power of 2, which equals 25/36. Solving the square root of both sides gives (V minus 7) divided by V equals 5/6. Cross-multiplying yields 6V minus 42 equals 5V, so the total capacity of the container is 42 L.

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