SOLUTION: By weight,one fertilizer is 10% potassium, 40% nitrogen and 50% phosphorous. A second fertilizer has percents 10, 20 & 70, respectively and a third fertilizer has percents of 0, 40

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Question 630935: By weight,one fertilizer is 10% potassium, 40% nitrogen and 50% phosphorous. A second fertilizer has percents 10, 20 & 70, respectively and a third fertilizer has percents of 0, 40, and 60 respectively. How much of each must be mixed to get 200 lbs of fertilizer with percents of 8, 30 & 62, respectively?
___ lbs of first mixture
___ lbs of second mixture
___ lbs of third mixture
Answer by josmiceli(19441) (Show Source):
You can put this solution on YOUR website!
pounds of potassium total
pounds of nitrogen total
pounds of phosphorus total
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Let = weight in pounds of 1st fertilizer
Let = weight in pounds of 2nd fertilizer
Let = weight in pounds of 3rd fertilizer
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(1)
(2)
(3)
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(1)
Substitute this into (2)
(2)
(2)
(2)
(2)
(2)
Substitute (1) and (2) into (3)
(3)
(3)
(3)
(3)
(3)
and
(1)
(1)
(1)
and
(2)
(2)
(2)
60 pounds of 1st fertilizer are needed
100 pounds of 2nd fertilizer are needed
40 pounds of 3rd fertilizer are needed
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You can check like this:

OK- you can check (2) and (3)