SOLUTION: A farmer needs 120 gallons of an 18% nitrogen fertilizer. But the farmer only has 10% nitrogen and 22% nitrogen fertilizer. How much of each fertilizer does the farmer need to mix?

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Question 188470: A farmer needs 120 gallons of an 18% nitrogen fertilizer. But the farmer only has 10% nitrogen and 22% nitrogen fertilizer. How much of each fertilizer does the farmer need to mix?
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
A farmer needs 120 gallons of an 18% nitrogen fertilizer. But the farmer only has 10% nitrogen and 22% nitrogen fertilizer. How much of each fertilizer does the farmer need to mix?
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Equation:
nitro + nitro = nitro
0.10x + 0.0.22(120-x) = 0.18*120
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Multiply thru by 100 to get:
10x + 22*120 - 22x = 18*120
-12x = -4*120
x = 40 gallons (amt. of 10% solution needed )
120-x = 80 gallons (amt. of 22% solution needed)
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Cheers,
Stan H.