<PRE><B>Question 233503</B>
regular milk has 4% butterfat. how many litres of regular milk must be mixed with 40L of milk with 1% butterfat to have milk with 2% butterfat? 
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Equation:
fat + fat = fat
0.04x + 0.01(40) = 0.02(x+40)
Multiply thru by 100 to get:
4x + 40 = 2x + 80
2x = 40
x = 20L (amount of regular mild needed in the mixture)
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Cheers,
Stan H.</PRE>