SOLUTION: A certain metal is 40% copper. How many kilograms of this metal must be mixed with 60 kilograms of a metal that is 70% copper to get a metal that is 50% copper?

Question 651004:
A certain metal is 40% copper. How many kilograms of this metal must be mixed with 60 kilograms of a metal that is 70% copper to get a metal that is 50% copper?
Found 2 solutions by josmiceli, lwsshak3:
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
Let = kg of 40% metal needed
= kg of copper in 40% metal
kg of copper in 70% metal

120 kg of the 40% metal are needed
check:

OK

Answer by lwsshak3(11628) (Show Source): You can put this solution on YOUR website!
A certain metal is 40% copper. How many kilograms of this metal must be mixed with 60 kilograms of a metal that is 70% copper to get a metal that is 50% copper?
**
let x=kg of 40% copper to be mixed
x+60=kg of 50% mixture
..
40%x+70%*60=50%(x+60)
.4x+42=.5x+30
.1x=12
x=120
kg of 40% copper to be mixed=120
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