A dairy needs 360 gallons of milk containing 7% butterfat. How many gallons each of milk containing 9% butterfat and milk containing 3% butterfat must be used to obtain the desired 360 gallons?
Let the number of gallons of 9% butterfat ==G
The number of gallons of 3% butterfat ==360 - G
0.09G + 0.03[360 - G] ==0.07 * 360
0.09G + 10.8 - 0.03G ==25.2
0.06G ==25.2 - 10.8 == 14.4
G ==14.4 /0.06==240 gallons of 9% butterfat will be needed
360 240 ==120 Gallons of 3% butterfat will be needed.
