SOLUTION: Forty liters of a 60% salt solution are diluted to produce a 45% solution. How much must be drained and replaced with distilled water so that the resulting solution will contain on

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Question 961475: Forty liters of a 60% salt solution are diluted to produce a 45% solution. How much must be drained and replaced with distilled water so that the resulting solution will contain only 45% salt?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +x+ = liters of 60% solution to be
drain off and replaced with water
------------------------------------
+.6x+ = liters of salt in the 60% solution
that is drained off
--------------------------------------
+.6%2A40+=+24+ liters of salt to begin with
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+%28+24+-+.6x+%29+%2F+40+=+.45+
+24+-+.6x+=+.45%2A40+
+24+-+.6x+=+18+
+.6x+=+24+-+18+
+.6x+=+6+
+x+=+10+
--------------
10 liters of solution should be drained off
and replaced with water
----------------------
check answer:
The total water you end up with is:
+.4%2A%28+40+-+x+%29+=+.4%2A%28+40+-+10+%29+
+.4%2A30+=+12+ liters
plus the +10+ I added = +22+ liters of water
I've still got +40+ liters total, so my concentration is:
+%28+40+-+22+%29+%2F+40+
+18%2F40+=+.45+
OK