Question

A 12 litre solution is `33(1)/(2)` acid. How much water must be added to get the solution having 20% acid?

Answer 1

Let the amount of water be x litres.
Volume of acid in the solution

= `33(1)/(3)%` of 12 litres

= `(100)/(3)`% x 12

= `(100)/(300) xx12`
= 4litres
Concentration of acid in (12 + x)litres of solution = 20%

⇒ `(4)/(12 + x) = (20)/(100)`

⇒ `(4)/(12 + x) = (1)/(5)`
⇒ 12 + x = 20
⇒ x = 8litres
Hence, 8litres of water should be added.