SOLUTION: An engineer wants to make a 60% cement mixture. How many pounds of an 80% cement mixture must she mix with 14 pounds of a 50% mixture to create a 60% cement mixture?

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Question 749867: An engineer wants to make a 60% cement mixture. How many pounds of an 80% cement mixture must she mix with 14 pounds of a 50% mixture to create a 60% cement mixture?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Pounds of cement in 50% mix = +.5%2A14+=+7+
Let +x+ = pounds of 80% mix needed
+.8x+ = pounds of cement in 80% mix
-----------------------------------
+%28+7+%2B+.8x+%29+%2F+%28+14+%2B+x+%29+=+.6+
+7+%2B+.8x+=+.6%2A%28+14+%2B+x+%29+
+7+%2B+.8x+=+8.4++%2B+.6x+
+.2x+=+1.4+
+x+=+7+
7 pounds of 80% mix are needed
check:
+%28+7+%2B+.8x+%29+%2F+%28+14+%2B+x+%29+=+.6+
+%28+7+%2B+.8%2A7+%29+%2F+%28+14+%2B+7+%29+=+.6+
+12.6+%2F+21+=+.6+
+12.6+=+.6%2A21+
+12.6+=+12.6+
OK