Iate half an apple pie on Saturday and two thirds of the remainder on Sunday. What fraction of the pie was left for Monday?　 
Overseas Competition->Knowledge Point->Word Problem Modules->Solving Problems Involving Fractions and Percentages->Understanding the Base
After I eat one half, half of the apple pie is left. Eating two thirds of this half leaves one third of one half of the pie, which is one sixth, for Monday. 