SOLUTION: A metallurgit needs to make 3 oz of an alloy containing 76%platinum. She isgoing to melt and combine one metal that is 90% platinum and one that is 70% platinum. How much of eac

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Question 163788: A metallurgit needs to make 3 oz of an alloy containing 76%platinum. She isgoing to melt and combine one metal that is 90% platinum and one that is 70% platinum. How much of each should she use?
Answer by jojo14344(1513) About Me  (Show Source):
You can put this solution on YOUR website!

Remember:
x=amount of 90% platinum
y=amount of 70% platinum
So, x%2By=3oz --------------------> eqn 1
We get in eqn 1,
y=3-x --------------------------> eqn 2
Also,
0.90x%2B0.70y=3oz%280.76%29 ----------> eqn 3
Susbt eqn 2 in eqn 3:
0.90x%2B0.70%283-x%29=2.28
0.90x%2B2.10-0.70x=2.28
0.20x=2.28-2.10=0.18
cross%280.20%29x%2Fcross%280.20%29=cross%280.18%290.90%2Fcross%280.20%29
x=0.90oz, for 90%
Via eqn 2:
y=3-0.90=2.10oz, for 70%
Check via eqn 3,
0.90%280.90%29%2B0.70%282.10%29=3%280.76%29
0.81%2B1.47=2.28
2.28=2.28
Thank you,
Jojo