Multiple choice

The composition of a solution is 5% salt by weight. How many kg of fresh water must be mixed with 120 kg of the solution for the content of salt in the solution to be made 3%?

  1. 60 kg

  2. 70 kg

  3. 80 kg

  4. 90 kg

  5. 100 kg
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The amount of salt remains constant. Initially, salt = 5% of 120 kg = 6 kg. Let x be the amount of water added. New total weight = 120 + x. We want 6 / (120 + x) = 3 / 100. Solving for x: 600 = 360 + 3x, so 3x = 240, x = 80 kg.

AI explanation

Using the rule of alligation for fresh water, which has 0 percent salt, and the solution, which has 5 percent salt, the ratio of fresh water to the solution is (5 minus 3) to (3 minus 0). This ratio is 2 to 3. If 3 parts equal 120 kg, then 1 part is 40 kg, meaning the required 2 parts of fresh water equal 80 kg.

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