$$\dfrac{1}{2}$$ of the pens in a box are red, $$\dfrac{1}{4}$$ of the remainder are blue and the rest are green. What percentage of the pens in the box are green? 
Overseas In-curriculum->Knowledge Point->Operations of Numbers ->Word Problems Involving Fractions and Percentages->Finding the Percentage Given a Part and a Whole Overseas Competition->Knowledge Point->Counting Modules
Remainder $=1-\frac{1}{2}=\frac{1}{2}$  Green $=1-\frac{1}{4}=\frac{3}{4}$ of remainder  $=\frac{3}{4}\times\frac{1}{2}$ of total  $=\frac{3}{8}$ of total  $=\frac{3}{8}\times100\textbackslash\%=37.5\textbackslash\%$ of total 