AMC 10 2008a Problem 2

A square is drawn inside a rectangle. The ratio of the width of the rectangle to a side of the square is $2:1$. The ratio of the rectangle's length to its width is $2:1$. What percent of the rectangle's area is inside the square? $\mathrm{(A)}\ 12.5 \mathrm{(B)}\ 25 \mathrm{(C)}\ 50 \mathrm{(D)}\ 75 \mathrm{(E)}\ 87.5$