SOLUTION: This is a weighted average word problem, that i really need the answer to: whipping cream contains 9% butter fat. 2% milk contains 2% butterfat. How much whipping cream and 2% mi

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Question 281130: This is a weighted average word problem, that i really need the answer to:
whipping cream contains 9% butter fat. 2% milk contains 2% butterfat.
How much whipping cream and 2% milk should be mixed to obtain 35 gallons of milk with 4% butterfat?
Answer by Fombitz(13828) About Me  (Show Source):
You can put this solution on YOUR website!
Let the amount of whipping cream be W and let the amount of 2% milk be T.
1.W%2BT=35 - Volume equation
2.9W%2B2T=4%2A%28W%2BT%29=4%2835%29=140 - Concentration equation
Use eq. 1 to solve for W in terms of T.
W%2BT=35
W=35-T
Now substitute into eq. 2 and solve for T.
9W%2B2T=140
9%2835-T%29%2B2T=140
315-9T%2B2T=140
-7T=-175
T=25
Then from eq. 1,
W=35-T=35-25=10
10 gallons of whipping cream and 25 gallons of 2% milk.