Question

if a bottle holding 3 liters of milk contains 3.5% butterfat,How much skimmed milk must be added to dilute the milk to 2% butterfat

Answer 1

amount of skimmed milk added --- x L

.035(3) +0.0x = .02(x+3)
.105 = .02x + .06
.02x = .045
x = 2.25

add 2.25 L

check:
3.5% of 3 L is .105 L of fat
adding 2.25 L of no fat milk gives us
5.25 L containing still only .105 fat
rate of fat = .105/5.25 = .02 as required