Question

A vat contains 60 gallons of a 15% saline solution. How many gallons of water must be evaporated so that the resulting solution will be 20% saline?

Answer 1

To solve this problem we can use proportion.
60 gallons -----------100%
x-------------------------15%

`x= (60*15)/(100) = 9` gallons of saline.
Now we can use this knowledge and create second proportion
9 galllons -------------20%
x-------------------------100%


`x= (9*100)/(20)=45` galloons
Now we can just find the difference (evaporated gallons)
60-45=15 - its our result.