Question 682079
Here is my problem as written in my homework:
A metallurgist needs to produce 10kg of an alloy which is 65% copper and 35% tin. He has an alloy which is 50% copper and 50% tin. How much of this 50-50 alloy must he melt together with pure copper to make the desired alloy? How much pure copper must he use? 
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let x=amt of pure copper to be melted with 50-50 alloy
10-x=amt of 50-50 alloy to be melted with pure copper
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100%*x+50%*(10-x)=65%*10
x+(10-x)/2=6.5
2x+10-x=2*6.5=13
x+10=13
x=3
10-x=7
amt of pure copper to be melted with 50-50 alloy=3kg
amt of 50-50 alloy to be melted with pure copper=7kg