Let's assume that after n iteration, the volume of the milk will be less than 50%, which is less than 20 liters. Initially, the amount of milk is 40 liters, after the first iteration, the volume of milk is 40⋅
9
10
After the second iteration, the volume of milk is 40×(
9
10
)2 Similarly, after the n iterations, the volume of milk is 40×(