A container has 60 litres of a mixture of acid and water in the ratio 7:3. 20% of the mixture is taken out and replaced with water. This operation is repeated once more. What is the final percentage of acid in the mixture?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 44.8%
Initial mixture = 60 litres
Ratio of acid : water = 7 : 3
Initial acid = 60 × 7/10 = 42 litres
Initial water = 60 × 3/10 = 18 litres
20% of mixture removed each time = 60 × 20/100 = 12 litres
After first replacement:
Acid removed = 42 × 12/60 = 8.4 litres
Remaining acid = 42 − 8.4 = 33.6 litres
Water added = 12 litres
Total mixture again = 60 litres
After second replacement:
Acid removed = 33.6 × 12/60 = 6.72 litres
Remaining acid = 33.6 − 6.72 = 26.88 litres
Final percentage of acid = (26.88/60) × 100 = 44.8%
Therefore, the final percentage of acid is 44.8%.