SOLUTION: A farmer has two types of milk, one that is 24% butterfat and another which is 18% butterfat. How much of each should he use to end up with 42 gallons of 20% butterfat?

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Question 1130677: A farmer has two types of milk, one that is 24% butterfat and another which is 18% butterfat. How much of each should he use to end up with 42 gallons of 20% butterfat?
Answer by addingup(3677) About Me  (Show Source):
You can put this solution on YOUR website!
x = 24%
y = 18%
.
x + y = 42 therefore y = 42 - x
0.24x + 0.18y = 0.20(42) substitute for y:
0.24x + 0.18(42 - x) = 8.4
0.24x + 7.56 - 0.18x = 8.4
0.06x = 0.84
x = 14
He should use 14 gallons of the 24% butterfat and (42-14= 28) 28 gallons of the 18% to get 42 gallons of 20%