<PRE><B>Question 819020</B>
A chemist has 100 liters of 30% sodium chloride solution. She intends to drain a certain number of liters and replace with a more concentrated solution. 
a) How much of this solution should she drain and replace with 80% sodium chloride if she wants a 55% sodium chloride solution?
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sc - sc + sc = sc
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0.30*100 - 0.30x + 1*x = 0.80*100
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Multiply thru by 100 to get::
30*100 - 30x + 100x = 80*100
70x = 50*100
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x = 7.14 liters (amt of liquid to remove and replace.
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Cheers,
Stan H.
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