A dairy needs 332 gallons of milk containing 6% butterfat. How many gallons each of milk containing 7% butterfat and milk containing 3% butterfat must be used to obtain the desired 332 gallons?

249 gallons of 7% butterfat milk and 83 gallons of 3% butterfat milk

Step-by-step explanation:

If x is the gallons of 7% butterfat milk, and y is the gallons of 3% butterfat milk, then:

x + y = 332

0.07x + 0.03y = 0.06 (332)

Solve the system of equations using substitution:

0.07x + 0.03 (332 - x) = 0.06 (332)

0.07x + 9.96 - 0.03x = 19.92

0.04x = 9.96

x = 249

y = 332 - x

y = 83

You need 249 gallons of 7% butterfat milk and 83 gallons of 3% butterfat milk.