SOLUTION: This is a real problem. I make cast bullets from various mixtures of lead (Pb), tin (Sn) and antimony (An).I have a one-pound piece of Pb-Sn mixture, 30% tin and 70% lead. I want

Algebra ->  Customizable Word Problem Solvers  -> Mixtures -> SOLUTION: This is a real problem. I make cast bullets from various mixtures of lead (Pb), tin (Sn) and antimony (An).I have a one-pound piece of Pb-Sn mixture, 30% tin and 70% lead. I want      Log On

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Question 720744: This is a real problem. I make cast bullets from various mixtures of lead (Pb), tin (Sn) and antimony (An).I have a one-pound piece of Pb-Sn mixture, 30% tin and 70% lead. I want to know how much lead I have to add to the one-pound piece to make the mixture 4% tin and 96% lead.
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Be careful with those bullets- just kidding
Let +x+ = pounds of lead to be added to mixture
You start out with:
+.3%2A1+=+.3+ pounds of tin
+.7%2A1+=+.7+ pounds of lead
------------
( total pounds of lead ) / ( total pounds of metal ) = .96
+%28+.7+%2B+x+%29+%2F+%28+1+%2B+x+%29+=+.96+
+.7+%2B+x+=+.96%2A%28+1+%2B+x+%29+
+.7+%2B+x+=+.96+%2B+.96x+
+.04x+=+.96+-+.7+
+.04x+=+.26++
+x+=+6.5+
If you add 6.5 pounds of lead, you will have
4% tin, 96% lead
check:
+%28+.7+%2B+x+%29+%2F+%28+1+%2B+x+%29+=+.96+
+%28+.7+%2B+6.5+%29+%2F+%28+1+%2B+6.5+%29+=+.96+
+7.2+%2F+7.5+=+.96+
+7.2+=+.96%2A7.5+
+7.2+=+7.2+
OK