Here is a real problem, slightly harder. A container which can hold 60 liters contains water and oil, 30 liters of oil and 30 liters of water. Some of the properties of oil and water when put together: Oil floats on water Oil and water cannot visually be distinguished. Oil and water do not mix. There are three other containers which can measure 43 liters, 11 liters, and 7 liters. How do you separate oil from water completely? *There is no trick with words here. It is just some number manipulation.