At a cafeteria, the automatic ice machine can completely fill itself in 20 minutes. During lunch time, customers can completely empty the ice machine in 30 minutes. At the start of lunch time, the ice machine is completely and it starts making ice at the same time that customers start taking ice. How long will it take for the machine to be completely full? (Hint: The customers take away the ice.)
a. 12 minutes. b. 30 minutes
c. 20 minutes. d. 60 minutes
2 answers