SOLUTION: A metalworker has a metal alloy that is 20​% copper and another alloy that is 70​% copper. How many kilograms of each alloy should the metalworker combine to create 90

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Question 1108002: A metalworker has a metal alloy that is 20​% copper and another alloy that is 70​% copper. How many kilograms of each alloy should the metalworker combine to create 90 kg of a 50​% copper​ alloy?
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
A metalworker has a metal alloy that is 20​% copper and another alloy that is 70​% copper. How many kilograms of each alloy should the metalworker combine to create 90 kg of a 50​% copper​ alloy?
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Quantity Eq:: t + s = 90 kg
Copper Eq:: 0.2t+0.7s = 0.5*90
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Modify::
t + s = 90
2t + 7s = 5*90
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Modify for elimination::
2t + 2s = 2*90
2t + 7s = 5*90
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Subtract and solve for "s":
5s = 3*90
s = 3*18
s = 54 kg (amt. of 7% alloy needed)
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t = 90-s = 36 kg (amt. of 20% alloy needed)
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Cheers,
Stan H.
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