Multiple choice

A container has 30 litres of water. 3 litres of the mixture is taken out and replaced with 3 litres of spirit. If this process is carried out twice in total, what will be the quantity of water left in the final mixture?

  1. 24 litres

  2. 23 litres

  3. 24.3 litres

  4. 23.3 litres

  5. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Using the formula for replacement: Final amount = Initial * (1 - removed/total)^n. Here, 30 * (1 - 3/30)^2 = 30 * (0.9)^2 = 30 * 0.81 = 24.3 litres.

AI explanation

Using the mixture replacement formula, the final amount of the original liquid equals the initial amount multiplied by the fraction retained raised to the number of operations. The initial amount of water is 30 litres, the fraction retained after removing 3 litres is 27/30 or 9/10, and the operation is performed twice. Thus, the quantity of water left is 30 multiplied by (9/10) squared, which is 30 multiplied by 81/100, yielding 24.3 litres.

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