SOLUTION: How much pure antifreeze needs to be added to 15 gallons of 40% antifreeze solution to make a 50% solution

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Question 921722: How much pure antifreeze needs to be added to 15 gallons of 40% antifreeze solution to make a 50% solution
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +x+ = gallons of pure antifreeze to be added
+.4%2A15+=+6+ gallons of antifreeze in 40% mixture
-----------------
+%28+x+%2B+6+%29+%2F+%28+x+%2B+15+%29+=+.5+
+x+%2B+6+=+.5%2A%28+x+%2B+15+%29+
+x+%2B+6=+.5x+%2B+7.5+
+.5x+=+1.5+
+x+=+3+
3 gallons of pure antifreeze must be added
check:
+%28+x+%2B+6+%29+%2F+%28+x+%2B+15+%29+=+.5+
+%28+3+%2B+6+%29+%2F+%28+3+%2B+15+%29+=+.5+
+9+%2F+18+=+.5+
+.5+=+.5+
OK