SOLUTION: how many gallons of 80% acid solution must be mixed with 40 gallons of 13% solution to obtain a 70% acid

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Question 698154: how many gallons of 80% acid solution must be mixed with 40 gallons of 13% solution to obtain a 70% acid
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +a+ = gallons of 80% solution needed
+.8a+ = gallons of acid in 80% solution
+.13%2A40+=+5.2+ gallons of acid in 13% solution
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+%28+.8a+%2B+5.2+%29+%2F+%28+a+%2B+40+%29+=+.7+
+.8a+%2B+5.2+=+.7%2A%28+a+%2B+40+%29+
+.8a+%2B+5.2+=+.7a+%2B+28+
+.1a+=+22.8+
+a+=+228+
228 gallons of 80% acid solution must be added
check the answer:
+%28+.8a+%2B+5.2+%29+%2F+%28+a+%2B+40+%29+=+.7+
+%28+.8%2A228+%2B+5.2+%29+%2F+%28+228+%2B+40+%29+=+.7+
+%28+182.4+%2B+5.2+%29+%2F+268+=+.7+
+187.6+%2F+268+=+.7+
+187.6+=+.7%2A268+
+187.6+=+187.6+
OK