Doan mixes together 1 litre of 1% butterfat milk, 2 litres of 2% butterfat milk and 4 litres of 4% butterfat milk. What percentage of the resulting seven litres of milk is butterfat?
+36916 sum of ingredients = final ingredients
1%(1liter) = .01 (1) 2% of 2 liters = .02(2)
.01(1) + .02(2) + .04(4) = x (7 liters) solve for x = .03 or 3%
