SOLUTION: an alloy of iron contains 49% iron while another alloy contains 28% iron. how many kg of each alloy should be used to get 120 kg of 42% iron alloy ?

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Question 615150: an alloy of iron contains 49% iron while another alloy contains 28% iron. how many kg of each alloy should be used to get 120 kg of 42% iron alloy ?
Answer by Alan3354(69443) About Me  (Show Source):
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an alloy of iron contains 49% iron while another alloy contains 28% iron. how many kg of each alloy should be used to get 120 kg of 42% iron alloy ?
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Do it like this:
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if a 14% acid solution is mixed with a 19% acid solution to produce 45 gallons of a 15% acid solution how much (in gallons) of each solution should be used?
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f = 14%
n = 19%
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f + n = 45 (total gallons)
14f + 19n = 15*45 (total acid)
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n = 45 - f
Sub for n
14f + 19*(45-f) = 675
14f + 855 - 19f = 675
-5f = -180
f = 36 gallons of 14%
n = 9 gallons of 19%