SOLUTION: How many pounds of a 70% copper alloy must be melted with how many pounds of a 90% copper alloy to obtain 100 pounds of an 81% copper alloy?

Question 855796: How many pounds of a 70% copper alloy must be melted with how many pounds of a 90% copper alloy to obtain 100 pounds of an 81% copper alloy?
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
Let = pounds of 70% alloy needed
Let = pounds of 90% alloy needed
------------------------------------
(1)
(2)
-------------------------------
(2)
(2)
----------------------
Multiply both sides of (1) by
and subtract (1) from (2)
(2)
(1)

and
(1)

-------------------
45 pounds of 70% alloy are needed
55 pounds of 90% alloy are needed
check:
(2)
(2)
(2)
(2)
OK

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