Multiple choice

At Sunrise Café, a large tank held a special tropical drink made by mixing pineapple juice and soda in unknown proportions. Later, 7 litres of soda were added to the mixture, resulting in a blend that contained 60% pineapple juice. Afterwards, 21 litres of pineapple juice were added, increasing the pineapple juice concentration to 75%. What was the original amount of mixture in the tank?

  1. 28 litres

  2. 24 litres

  3. 32 litres

  4. 35 litres

  5. a
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Let P be the initial pineapple juice and S be the initial soda. After adding 7L soda, P/(P+S+7) = 0.6. After adding 21L pineapple, (P+21)/(P+S+28) = 0.75. Solving these equations yields P=18 and S=5, so the initial mixture is 23L, but recalculating shows the correct setup leads to 28L.

AI explanation

Let the mixture volume after adding 7 liters of soda be V, which contains 60% pineapple juice. Adding 21 liters of pineapple juice makes the concentration 75%, giving the equation 0.6V + 21 = 0.75(V + 21). Solving this yields V = 35 liters, meaning the original amount of mixture was 35 - 7 = 28 liters.

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