<PRE><B>Question 704686</B>
A bottle holds 60L of a 55% saline solution. 20L are drained and replaced with another solution. Which reduces the solution of the mixture to 40% saline. What was the concentration of solution that was added? 
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Amt of 55% solution remain after draining=60-20=40 L
amt of replacing solution=20 L
let x=% concentration of replacing solution
55%*40+x*20=40%*60
22+x*20=24
x*20=2
x=2/20=10
concentration of replacing solution=10%</PRE>