Question 100891
A 20 gallon salt solution is 30% salt. What is the greatest number of gallons of water that can be evaporated so the solution is still less than 45% salt?
:
Let x = amt of water evaporated to provide a 45% solution

.3(20) < .45(20-x)
:
6 - < 9 - .45x
:
+.45x < 9 - 6
:
.45x < 3
:
x < 3/.45
:
x < 6{{{2/3}}} gal evaporated to maintain less than a 45% solution
:
:
Check by finding salt content in the two amts:
 .3(20) = .45(20 - 6{{{2/3}}})
  6  = .45 * 13{{{1/3}}}
  6  =  6