You can put this solution on YOUR website! Let = liters of 1% milk needed
Let = liters of 4% milk needed = liters of fat in 1% milk = liters of fat in 4% milk
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(1)
(2)
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(2)
(2)
(2)
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Subtract (1) from (2)
(2)
(1)
and, since
(1)
(1)
(1)
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40 liters of 1% milk are needed
20 liters of 4% milk are needed
check:
(2)
(2)
(2)
(2)
(2)
OK