SOLUTION: How many gallons of a 10% salt solution must be added to a 15 gallons of a 20% salt solution to obtain a 16% solution?

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Question 957722: How many gallons of a 10% salt solution must be added to a 15 gallons of a 20% salt solution to obtain a 16% solution?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +x+ = gallons of 10% solution needed
+.1x+ = gallons of salt in 10% solution
+.2%2A15+=+3+ gallons of salt in 20% solution
---------------------
+%28+.1x+%2B+3+%29+%2F+%28+x+%2B+15+%29+=+.16+
+.1x+%2B+3+=+.16%2A%28+x+%2B+15+%29+
+.1x+%2B+3+=+.16x+%2B+2.4+
+.06x+=+.6+
+x+=+10+
10 gallons of 10% solution are needed
check:
+%28+.1x+%2B+3+%29+%2F+%28+x+%2B+15+%29+=+.16+
+%28+.1%2A10+%2B+3+%29+%2F+%28+10+%2B+15+%29+=+.16+
+4+%2F+25+=+.16+
+4+=+4+
OK