Question

A 90 kg solution has 10% salt. How much water must be evaporated to have the solution with 20% salt?

Answer 1

Quantity of solution = 90kg

Quantity of salt 

= `90"kg" xx (10)/(100)`
= 9kg
Let x kg of water be ecaporated.
Therefore,

`(9)/(90 - x) = (20)/(100)`

⇒ 900 - 1800 - 20x
⇒ 20x = 900
⇒ x = 45
Therefore, 45kg of water must be evaporated.