<PRE><B>Question 337983</B>
How much water must be evaporated from 500 grams of a 10% salt solution
to obtain a 15% salt solution?
;
Let w = amt of water to be evaporated
:
Write an amt of salt equation (the amt remains the same, only the % changes)
.10(500) = .15(500-w)
50 = 75 - .15w
.15w = 75 - 50
w = {{{25/.15}}}
w = 166{{{2/3}}} grams to be evaporated 
:
:
Check: That leaves: 500 - 166.67 =  333.33 gram solution after evaporation
.10(500) = .15(333.33)
50 = 50; confirms our answer </PRE>