Multiple choice

Two solutions of $90\%$ and $97\%$ purity are mixed resulting in $21$ litres of mixture of $94\%$ purity. How much is the quantity of the first solution in the resulting mixture?

  1. $15$ liters
  2. $12$ liters
  3. $9$ liters
  4. $6$ liters
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Using the alligation rule: (97 - 94) / (94 - 90) = 3 / 4. The ratio of the first solution to the second is 3:4. Total parts = 7. Quantity of first solution = (3/7) * 21 = 9 liters.

AI explanation

Using the rule of alligation, the ratio of the first solution to the second solution is (97 - 94) : (94 - 90), which simplifies to 3 : 4. This means the total 21 litres is divided into 7 equal parts, with the first solution accounting for 3 parts. The quantity of the first solution is (3/7) multiplied by 21, which equals 9 litres.