20 litres of mixture of acid and water contain 10% water. How much water should be added so that percentage of water becomes 20% in this mixture? Choose one.
A) 2 l
B) 3 l
C) 2.5 l
D) 4 l
E) 5 l

Rationale: total mixture = 20 ltr water contain = 10 % of 20 ltr = > 2 ltr water it means 18 ltr is acid in that mixture we have to make 20 % water so . . 20 % of 20 = 4 ltr water must be there in the new mixture we have already 2 ltr water so we have to add 2 ltr more answer : a
Answer: A