SOLUTION: how many quarts of pure antifreeze must be added to 8 quarts of a 10% solution to obtain a 20% antifreeze solution?

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Question 941971: how many quarts of pure antifreeze must be added to 8 quarts of a 10% solution to obtain a 20% antifreeze solution?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +x+ = quarts of pure antifreeze needed
+.1%2A8+=+.8+ = quarts of antifreeze in 10% solution
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+%28+x+%2B+.8+%29+%2F+%28+x+%2B+8+%29+=+.2+
+x+%2B+.8+=+.2%2A%28+x+%2B8+%29+
+x+%2B+.8+=+.2x+%2B+1.6+
+.8x+=+.8+
+x+=+1+
1 quart of pure antifreeze is needed
check:
+%28+x+%2B+.8+%29+%2F+%28+x+%2B+8+%29+=+.2+
+%28+1+%2B+.8+%29+%2F+%28+1+%2B+8+%29+=+.2+
+1.8+%2F+9+=+.2+
+1.8+=+.2%2A9+
+1.8+=+1.8+
OK