SOLUTION: How many liters of a 20% alcohol solution must be mixed with 60 liters of a 90% solution to get a 70% solution?

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Question 525770: How many liters of a 20% alcohol solution must be mixed with 60 liters of a 90% solution to get a 70% solution?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
let x+ = liters of 20% solution needed
given:
+.9%2A60+=+54+ liters of alcohol in 90% solution
+.2x+ = liters of alcohol in 20% solution
---------------------------------
+%28+54+%2B+.2x+%29+%2F+%28+60+%2B+x+%29+=++.7+
+54+%2B+.2x+=+.7%2A%28+60+%2B+x+%29+
+54+%2B+.2x+=+42++%2B+.7x+
+.5x+=+12+
+x+=+24+
24 liters of 20% solution are needed
check answer:
+%28+54+%2B+.2x+%29+%2F+%28+60+%2B+x+%29+=++.7+
+%28+54+%2B+.2%2A24+%29+%2F+%28+60+%2B+24+%29+=++.7+
+%28+54+%2B+4.8+%29+%2F+84+=+.7+
+58.8+=+.7%2A84+
+58.8+=+58.8+
OK