document.write( "Question 94750: I have an algebra question for you, to which I require assistance, as I am not quite certain what it is they want me to do. It is a written question.\r
\n" ); document.write( "\n" ); document.write( "An alloy contains 60% by weight of copper, the remainder being zinc. How much copper must be mixed with 50kg of this alloy to give an alloy containing 75% copper?\r
\n" ); document.write( "\n" ); document.write( "I have done some nuber crunching and all I got was
\n" ); document.write( "60% of 50kg = 30kg
\n" ); document.write( "and
\n" ); document.write( "75% of 50kg = 37.5kg
\n" ); document.write( "and or
\n" ); document.write( "60x+40y=50
\n" ); document.write( "75x+25y=50 /5
\n" ); document.write( "60x+40y=50 /4
\n" ); document.write( "15x+5y=10
\n" ); document.write( "15x+10y=12.5
\n" ); document.write( "15x+5y=10
\n" ); document.write( "anyhow
\n" ); document.write( "X = .5kg
\n" ); document.write( "and
\n" ); document.write( "Y = .5kg
\n" ); document.write( "but it just does not look right, would you please be able to show me the correct way to sort this out. It would be greatly appreciated. Thank you. \n" ); document.write( "
Algebra.Com's Answer #68992 by Earlsdon(6294)\"\" \"About 
You can put this solution on YOUR website!
First, let's concentrate on the amount of copper (Cu) in the starting alloy and the resulting alloy.
\n" ); document.write( "The amount of copper in the starting alloy is: 60% of 50 kg or (0.6)(50). To this we want to add x kg of Cu to make (50+x) kg of an alloy, 75% of which is Cu. So we set up the equation:
\n" ); document.write( "(0.6)(50) + x = (0.75)(50+x) Simplify and solve for x.
\n" ); document.write( "30+x = 37.5+0.75x Subtract 0.75x from both sides.
\n" ); document.write( "30+0.25x = 37.5 Subtract 30 from both sides.
\n" ); document.write( "0.25x = 7.5 Finally, divide both sides by 0.25
\n" ); document.write( "x = 30
\n" ); document.write( "You would need to add 30kg of Cu to the 50kg of the starting alloy to obtain 80kg (50kg + 30kg) of the resulting alloy containing 75% Cu.\r
\n" ); document.write( "\n" ); document.write( "Check:
\n" ); document.write( "50(0.6)+30 = (50+30)(0.75)
\n" ); document.write( "30+30 = (80)(0.75)
\n" ); document.write( "60 = 60
\n" ); document.write( "
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